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19 Apr 2021 at 01:30
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Bibliography on: Pangenome


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RJR: Recommended Bibliography 19 Apr 2021 at 01:30 Created: 


Although the enforced stability of genomic content is ubiquitous among MCEs, the opposite is proving to be the case among prokaryotes, which exhibit remarkable and adaptive plasticity of genomic content. Early bacterial whole-genome sequencing efforts discovered that whenever a particular "species" was re-sequenced, new genes were found that had not been detected earlier — entirely new genes, not merely new alleles. This led to the concepts of the bacterial core-genome, the set of genes found in all members of a particular "species", and the flex-genome, the set of genes found in some, but not all members of the "species". Together these make up the species' pan-genome.

Created with PubMed® Query: pangenome or "pan-genome" or "pan genome" NOT pmcbook NOT ispreviousversion

Citations The Papers (from PubMed®)


RevDate: 2021-04-15

Gao G, Magadan S, Waldbieser GC, et al (2021)

A long reads-based de-novo assembly of the genome of the Arlee homozygous line reveals chromosomal rearrangements in rainbow trout.

G3 (Bethesda, Md.), 11(4):.

Currently, there is still a need to improve the contiguity of the rainbow trout reference genome and to use multiple genetic backgrounds that will represent the genetic diversity of this species. The Arlee doubled haploid line was originated from a domesticated hatchery strain that was originally collected from the northern California coast. The Canu pipeline was used to generate the Arlee line genome de-novo assembly from high coverage PacBio long-reads sequence data. The assembly was further improved with Bionano optical maps and Hi-C proximity ligation sequence data to generate 32 major scaffolds corresponding to the karyotype of the Arlee line (2 N = 64). It is composed of 938 scaffolds with N50 of 39.16 Mb and a total length of 2.33 Gb, of which ∼95% was in 32 chromosome sequences with only 438 gaps between contigs and scaffolds. In rainbow trout the haploid chromosome number can vary from 29 to 32. In the Arlee karyotype the haploid chromosome number is 32 because chromosomes Omy04, 14 and 25 are divided into six acrocentric chromosomes. Additional structural variations that were identified in the Arlee genome included the major inversions on chromosomes Omy05 and Omy20 and additional 15 smaller inversions that will require further validation. This is also the first rainbow trout genome assembly that includes a scaffold with the sex-determination gene (sdY) in the chromosome Y sequence. The utility of this genome assembly is shown through the improved annotation of the duplicated genome loci that harbor the IGH genes on chromosomes Omy12 and Omy13.

RevDate: 2021-04-14

Cui WJ, Zhang B, Zhao R, et al (2021)

Lineage-Specific Rewiring of Core Pathways Predating Innovation of Legume Nodules Shapes Symbiotic Efficiency.

mSystems, 6(2):.

The interkingdom coevolution innovated the rhizobium-legume symbiosis. The application of this nitrogen-fixing system in sustainable agriculture is usually impeded by incompatible interactions between partners. However, the progressive evolution of rhizobium-legume compatibility remains elusive. In this work, deletions of rhcV encoding a structural component of the type three secretion system allow related Sinorhizobium strains to nodulate a previously incompatible soybean cultivar (Glycine max). These rhcV mutants show low to medium to high symbiotic efficiency on the same cultivated soybean while being indistinguishable on wild soybean plants (Glycine soja). The dual pantranscriptomics reveals nodule-specific activation of core symbiosis genes of Sinorhizobium and Glycine genes associated with genome duplication events along the chronogram. Unexpectedly, symbiotic efficiency is in line with lineage-dependent transcriptional profiles of core pathways which predate the diversification of Fabaceae and Sinorhizobium. This is supported by further physiological and biochemical experiments. Particularly, low-efficiency nodules show disordered antioxidant activity and low-energy status, which restrict nitrogen fixation activity. Collectively, the ancient core pathways play a crucial role in optimizing the function of later-evolved mutualistic arsenals in the rhizobium-legume coevolution.IMPORTANCE Significant roles of complex extracellular microbiota in environmental adaptation of eukaryotes in ever-changing circumstances have been revealed. Given the intracellular infection ability, facultative endosymbionts can be considered pioneers within complex extracellular microbiota and are ideal organisms for understanding the early stage of interkingdom adaptation. This work reveals that the later innovation of key symbiotic arsenals and the lineage-specific network rewiring in ancient core pathways, predating the divergence of legumes and rhizobia, underline the progressive evolution of rhizobium-legume compatibility. This insight not only is significant for improving the application benefits of rhizobial inoculants in sustainable agriculture but also advances our general understanding of the interkingdom coevolution which is theoretically explored by all host-microbiota interactions.

RevDate: 2021-04-14

Jonkheer EM, Brankovics B, Houwers IM, et al (2021)

The Pectobacterium pangenome, with a focus on Pectobacterium brasiliense, shows a robust core and extensive exchange of genes from a shared gene pool.

BMC genomics, 22(1):265.

BACKGROUND: Bacterial plant pathogens of the Pectobacterium genus are responsible for a wide spectrum of diseases in plants, including important crops such as potato, tomato, lettuce, and banana. Investigation of the genetic diversity underlying virulence and host specificity can be performed at genome level by using a comprehensive comparative approach called pangenomics. A pangenomic approach, using newly developed functionalities in PanTools, was applied to analyze the complex phylogeny of the Pectobacterium genus. We specifically used the pangenome to investigate genetic differences between virulent and avirulent strains of P. brasiliense, a potato blackleg causing species dominantly present in Western Europe.

RESULTS: Here we generated a multilevel pangenome for Pectobacterium, comprising 197 strains across 19 species, including type strains, with a focus on P. brasiliense. The extensive phylogenetic analysis of the Pectobacterium genus showed robust distinct clades, with most detail provided by 452,388 parsimony-informative single-nucleotide polymorphisms identified in single-copy orthologs. The average Pectobacterium genome consists of 47% core genes, 1% unique genes, and 52% accessory genes. Using the pangenome, we zoomed in on differences between virulent and avirulent P. brasiliense strains and identified 86 genes associated to virulent strains. We found that the organization of genes is highly structured and linked with gene conservation, function, and transcriptional orientation.

CONCLUSION: The pangenome analysis demonstrates that evolution in Pectobacteria is a highly dynamic process, including gene acquisitions partly in clusters, genome rearrangements, and loss of genes. Pectobacterium species are typically not characterized by a set of species-specific genes, but instead present themselves using new gene combinations from the shared gene pool. A multilevel pangenomic approach, fusing DNA, protein, biological function, taxonomic group, and phenotypes, facilitates studies in a flexible taxonomic context.

RevDate: 2021-04-13

Machimbirike VI, Uthaipaisanwong P, Khunrae P, et al (2021)

Comparative genomics of Edwardsiella ictaluri revealed four distinct host-specific genotypes and thirteen potential vaccine candidates.

Genomics pii:S0888-7543(21)00142-7 [Epub ahead of print].

Edwardsiella ictaluri has been considered an important threat for catfish aquaculture industry for more than 4 decades and an emerging pathogen of farmed tilapia but only 9 sequenced genomes were publicly available. We hereby report two new complete genomes of E. ictaluri originated from diseased hybrid red tilapia (Oreochromis sp.) and striped catfish (Pangasianodon hypophthalmus) in South east Asia. E. ictaluri species has an open pan-genome consisting of 2615 core genes and 5592 pan genes. Phylogenetic analysis using core genome MLST (cgMLST) or based on ANI values consistently placed E. ictaluri isolates into 4 host-specific genotypes. Presence of unique genes and absence of certain genes from each genotype provided potential biomarkers for further development of genotyping scheme. Vaccine candidates with high antigenic, solubility and secretion probabilities were identified in silico from the core genes. Microevolution within the species is brought about by bacteriophages and insertion elements and possibly drive host adaptation.

RevDate: 2021-04-13

Lei L, Goltsman E, Goodstein D, et al (2021)

Plant Pan-Genomics Comes of Age.

Annual review of plant biology [Epub ahead of print].

A pan-genome is the nonredundant collection of genes and/or DNA sequences in a species. Numerous studies have shown that plant pan-genomes are typically much larger than the genome of any individual and that a sizable fraction of the genes in any individual are present in only some genomes. The construction and interpretation of plant pan-genomes are challenging due to the large size and repetitive content of plant genomes. Most pan-genomes are largely focused on nontransposable element protein coding genes because they are more easily analyzed and defined than noncoding and repetitive sequences. Nevertheless, noncoding and repetitive DNA play important roles in determining the phenotype and genome evolution. Fortunately, it is now feasible to make multiple high-quality genomes that can be used to construct high-resolution pan-genomes that capture all the variation. However, assembling, displaying, and interacting with such high-resolution pan-genomes will require the development of new tools. Expected final online publication date for the Annual Review of Plant Biology, Volume 72 is May 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

RevDate: 2021-04-12

Tang WT, Hao TW, GH Chen (2021)

Comparative Metabolic Modeling of Multiple Sulfate-reducing Prokaryotes Reveals Versatile Energy Conservation Mechanisms.

Biotechnology and bioengineering [Epub ahead of print].

Sulfate-reducing prokaryotes (SRPs) are crucial participants in the cycling of sulfur, carbon, and various metals in the natural environment and in engineered systems. Despite recent advances in genetics and molecular biology bringing a huge amount of information about the energy metabolism of SRPs, little effort has been made to link this important information with their biotechnological studies. This study aims to construct multiple metabolic models of SRPs that systematically compile genomic, genetic, biochemical, and molecular information about SRPs to study their energy metabolism. Pan-genome analysis was conducted to compare the genomes of SRPs, from which a list of orthologous genes related to central and energy metabolism was obtained. 24 SRP metabolic models via the inference of pan-genome analysis were efficiently constructed. The metabolic model of the well-studied model SRP Desulfovibrio vulgaris Hildenborough (DvH) was validated via Flux balance analysis (FBA). The DvH model predictions matched reported experimental growth and energy yields, which demonstrated that the core metabolic model worked successfully. Further, steady-state simulation of SRP metabolic models under different growth conditions showed how the use of different electron transfer pathways leads to energy generation. Three energy conservation mechanisms were identified, including menaquinone-based redox loop, hydrogen cycling, and proton pumping. Flavin-based electron bifurcation (FBEB) was also demonstrated to be an essential mechanism for supporting energy conservation. The developed models can be easily extended to other species of SRPs not examined in this study. More importantly, the present work develops an accurate and efficient approach for constructing metabolic models of multiple organisms, which can be applied to other critical microbes in environmental and industrial systems, thereby enabling the quantitative prediction of their metabolic behaviors to benefit relevant applications. This article is protected by copyright. All rights reserved.

RevDate: 2021-04-12

Zhong C, Chen C, Wang L, et al (2021)

Integrating pan-genome with metagenome for microbial community profiling.

Computational and structural biotechnology journal, 19:1458-1466 pii:S2001-0370(21)00072-6.

Advances in sequencing technology have led to the increased availability of genomes and metagenomes, which has greatly facilitated microbial pan-genome and metagenome analysis in the community. In line with this trend, studies on microbial genomes and phenotypes have gradually shifted from individuals to environmental communities. Pan-genomics and metagenomics are powerful strategies for in-depth profiling study of microbial communities. Pan-genomics focuses on genetic diversity, dynamics, and phylogeny at the multi-genome level, while metagenomics profiles the distribution and function of culture-free microbial communities in special environments. Combining pan-genome and metagenome analysis can reveal the microbial complicated connections from an individual complete genome to a mixture of genomes, thereby extending the catalog of traditional individual genomic profile to community microbial profile. Therefore, the combination of pan-genome and metagenome approaches has become a promising method to track the sources of various microbes and decipher the population-level evolution and ecosystem functions. This review summarized the pan-genome and metagenome approaches, the combined strategies of pan-genome and metagenome, and applications of these combined strategies in studies of microbial dynamics, evolution, and function in communities. We discussed emerging strategies for the study of microbial communities that integrate information in both pan-genome and metagenome. We emphasized studies in which the integrating pan-genome with metagenome approach improved the understanding of models of microbial community profiles, both structural and functional. Finally, we illustrated future perspectives of microbial community profile: more advanced analytical techniques, including big-data based artificial intelligence, will lead to an even better understanding of the patterns of microbial communities.

RevDate: 2021-04-12

Qureshi NA, Bakhtiar SM, Faheem M, et al (2021)

Genome-Based Drug Target Identification in Human Pathogen Streptococcus gallolyticus.

Frontiers in genetics, 12:564056.

Streptococcus gallolysticus (Sg) is an opportunistic Gram-positive, non-motile bacterium, which causes infective endocarditis, an inflammation of the inner lining of the heart. As Sg has acquired resistance with the available antibiotics, therefore, there is a dire need to find new therapeutic targets and potent drugs to prevent and treat this disease. In the current study, an in silico approach is utilized to link genomic data of Sg species with its proteome to identify putative therapeutic targets. A total of 1,138 core proteins have been identified using pan genomic approach. Further, using subtractive proteomic analysis, a set of 18 proteins, essential for bacteria and non-homologous to host (human), is identified. Out of these 18 proteins, 12 cytoplasmic proteins were selected as potential drug targets. These selected proteins were subjected to molecular docking against drug-like compounds retrieved from ZINC database. Furthermore, the top docked compounds with lower binding energy were identified. In this work, we have identified novel drug and vaccine targets against Sg, of which some have already been reported and validated in other species. Owing to the experimental validation, we believe our methodology and result are significant contribution for drug/vaccine target identification against Sg-caused infective endocarditis.

RevDate: 2021-04-12

Gómez P, Ruiz-Ripa L, Fernández-Fernández R, et al (2021)

Genomic Analysis of Staphylococcus aureus of the Lineage CC130, Including mecC-Carrying MRSA and MSSA Isolates Recovered of Animal, Human, and Environmental Origins.

Frontiers in microbiology, 12:655994.

Most methicillin resistant Staphylococcus aureus (MRSA) isolates harboring mecC gene belong to clonal complex CC130. This lineage has traditionally been regarded as animal-associated as it lacks the human specific immune evasion cluster (IEC), and has been recovered from a broad range of animal hosts. Nevertheless, sporadic mecC-MRSA human infections have been reported, with evidence of zoonotic transmission in some cases. The objective of this study was to investigate the whole-genome sequences of 18 S. aureus CC130 isolates [13 methicillin-resistant (mecC-MRSA) and five methicillin-susceptible (MSSA)] from different sequences types, obtained from a variety of host species and origins (human, livestock, wild birds and mammals, and water), and from different geographic locations, in order to identify characteristic markers and genomic features. Antibiotic resistance genes found among MRSA-CC130 were those associated with the SSCmecXI element. Most MRSA-CC130 strains carried a similar virulence gene profile. Additionally, six MRSA-CC130 possessed scn-sak and one MSSA-ST130 had lukMF'. The MSSA-ST700 strains were most divergent in their resistance and virulence genes. The pan-genome analysis showed that 29 genes were present solely in MRSA-CC130 (associated with SCCmecXI) and 21 among MSSA-CC130 isolates (associated with phages). The SCCmecXI, PBP3, GdpP, and AcrB were identical at the amino acid level in all strains, but some differences were found in PBP1, PBP2, PBP4, and YjbH proteins. An examination of the host markers showed that the 3' region of the bacteriophage φ3 was nearly identical to the reference sequence. Truncated hlb gene was also found in scn-negative strains (two of them carrying sak-type gene). The dtlB gene of wild rabbit isolates included novel mutations. The vwbp gene was found in the three MSSA-ST700 strains from small ruminants and in one MSSA-ST130 from a red deer; these strains also carried a scn-type gene, different from the human and equine variants. Finally, a phylogenetic analysis showed that the three MSSA-ST700 strains and the two MSSA-ST130 strains cluster separately from the remaining MRSA-CC130 strains with the etD2 gene as marker for the main lineage. The presence of the human IEC cluster in some mecC-MRSA-CC130 strains suggests that these isolates may have had a human origin.

RevDate: 2021-04-11

Ogg A, Vitulo N, Ecp M, et al (2021)

Pangenome analyses of LuxS-coding genes and enzymatic repertoires in cocoa-related lactic acid bacteria.

Genomics pii:S0888-7543(21)00136-1 [Epub ahead of print].

Lactobacillaceae presents potential for interspecific Quorum Sensing (QS) in spontaneous cocoa fermentation, correlated with high abundance of luxS. Three Brazilian isolates from cocoa fermentation were characterized by Whole Genome Sequencing and luxS gene was surveyed in their genomes, in comparison with public databases. They were classified as Lactiplantibacillus plantarum, Limosilactobacillus fermentum and Pediococcus acidilactici. LuxS genes were conserved in core genomes of the novel isolates, but in some non-cocoa related Lactic Acid Bacteria (LAB) it was accessory and plasmid-borne. The conservation and horizontal acquisition of luxS reinforces that QS is determinant for bacterial adaptation in several environments, especially taking into account the luxS has been correlated with modulation of bacteriocin production, stress tolerance and biofilm formation. Therefore, in this paper, new clade and species-specific primers were designed for future application for screening of luxSgene in LAB to evaluate the adaptive potential to diverse food fermentations.

RevDate: 2021-04-10

Shaw LP, Chau KK, Kavanagh J, et al (2021)

Niche and local geography shape the pangenome of wastewater- and livestock-associated Enterobacteriaceae.

Science advances, 7(15): pii:7/15/eabe3868.

Escherichia coli and other Enterobacteriaceae are diverse species with "open" pangenomes, where genes move intra- and interspecies via horizontal gene transfer. However, most analyses focus on clinical isolates. The pangenome dynamics of natural populations remain understudied, despite their suggested role as reservoirs for antimicrobial resistance (AMR) genes. Here, we analyze near-complete genomes for 827 Enterobacteriaceae (553 Escherichia and 274 non-Escherichia spp.) with 2292 circularized plasmids in total, collected from 19 locations (livestock farms and wastewater treatment works in the United Kingdom) within a 30-km radius at three time points over a year. We find different dynamics for chromosomal and plasmid-borne genes. Plasmids have a higher burden of AMR genes and insertion sequences, and AMR-gene-carrying plasmids show evidence of being under stronger selective pressure. Environmental niche and local geography both play a role in shaping plasmid dynamics. Our results highlight the importance of local strategies for controlling the spread of AMR.

RevDate: 2021-04-09

Min H, Baek K, Lee A, et al (2021)

Genomic characterization of four Escherichia coli strains isolated from oral lichen planus biopsies.

Journal of oral microbiology, 13(1):1905958.

Oral lichen planus (OLP) is a chronic T cell-mediated inflammatory disease that affects the mucus membrane of the oral cavity. We previously proposed a potential role of intracellular bacteria detected within OLP lesions in the pathogenesis of OLP and isolated four Escherichia coli strains from OLP tissues that were phylogenetically close to K-12 MG1655 strain. We sequenced the genomes of the four OLP-isolated E. coli strains and generated 6.71 Gbp of Illumina MiSeq data (166-195x coverage per strain). The size of the assembled draft genomes was 4.69 Mbp, with a GC content of 50.7%, in which 4360 to 4367 protein-coding sequences per strain were annotated. We also identified 368 virulence factors and 53 antibiotic resistance genes. Comparative genomics revealed that the OLP-isolated strains shared more pangenome orthologous groups with pathogenic strains than did the K-12 MG1655 strain, a derivative of K-12 strain isolated from human feces. Although the OLP-isolated strains did not have the major virulence factors (VFs) of the pathogenic strains, a number of VFs involved in adherence/invasion, colonization, or systemic infection were identified. The genomic characteristics of E. coli first isolated from the oral cavity would benefit future investigations on the pathogenic potential of these bacteria.

RevDate: 2021-04-06

Ye Q, Shang Y, Chen M, et al (2021)

Identification of Novel Sensitive and Reliable Serovar-Specific Targets for PCR Detection of Salmonella Serovars Hadar and Albany by Pan-Genome Analysis.

Frontiers in microbiology, 12:605984.

The accurate and rapid classification of Salmonella serovars is an essential focus for the identification of isolates involved in disease in humans and animals. The purpose of current research was to identify novel sensitive and reliable serovar-specific targets and to develop PCR method for Salmonella C2 serogroups (O:8 epitopes) in food samples to facilitate timely treatment. A total of 575 genomic sequences of 16 target serovars belonging to serogroup C2 and 150 genomic sequences of non-target serovars were analysed by pan-genome analysis. As a result, four and three specific genes were found for serovars Albany and Hadar, respectively. Primer sets for PCR targeting these serovar-specific genes were designed and evaluated based on their specificity; the results showed high specificity (100%). The sensitivity of the specific PCR was 2.8 × 101-103 CFU/mL and 2.3 × 103-104 CFU/mL for serovars Albany and Hadar, respectively, and the detection limits were 1.04 × 103-104 CFU/g and 1.16 × 104-105 CFU/g in artificially contaminated raw pork samples. Furthermore, the potential functions of these serovar-specific genes were analysed; all of the genes were functionally unknown, except for one specific serovar Albany gene known to be a encoded secreted protein and one specific gene for serovars Hadar and Albany that is a encoded membrane protein. Thus, these findings demonstrate that pan-genome analysis is a precious method for mining new high-quality serovar-targets for PCR assays or other molecular methods that are highly sensitive and can be used for rapid detection of Salmonella serovars.

RevDate: 2021-04-05

Calcino AD, Kenny NJ, M Gerdol (2021)

Single individual structural variant detection uncovers widespread hemizygosity in molluscs.

Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 376(1825):20200153.

The advent of complete genomic sequencing has opened a window into genomic phenomena obscured by fragmented assemblies. A good example of these is the existence of hemizygous regions of autosomal chromosomes, which can result in marked differences in gene content between individuals within species. While these hemizygous regions, and presence/absence variation of genes that can result, are well known in plants, firm evidence has only recently emerged for their existence in metazoans. Here, we use recently published, complete genomes from wild-caught molluscs to investigate the prevalence of hemizygosity across a well-known and ecologically important clade. We show that hemizygous regions are widespread in mollusc genomes, not clustered in individual chromosomes, and often contain genes linked to transposition, DNA repair and stress response. With targeted investigations of HSP70-12 and C1qDC, we also show how individual gene families are distributed within pan-genomes. This work suggests that extensive pan-genomes are widespread across the conchiferan Mollusca, and represent useful tools for genomic evolution, allowing the maintenance of additional genetic diversity within the population. As genomic sequencing and re-sequencing becomes more routine, the prevalence of hemizygosity, and its impact on selection and adaptation, are key targets for research across the tree of life. This article is part of the Theo Murphy meeting issue 'Molluscan genomics: broad insights and future directions for a neglected phylum'.

RevDate: 2021-04-04

Nousias O, F Montesanto (2021)

Metagenomic profiling of host-associated bacteria from 8 datasets of the red alga Porphyra purpurea with MetaPhlAn3.

Marine genomics pii:S1874-7787(21)00032-5 [Epub ahead of print].

Microbial communities play fundamental roles in association with marine algae; in fact, they are recognized to be actively involved in growth and morphogenesis of the algae. Porphyra purpurea is a red alga commonly found in the intertidal zone with a high economic value, however little is known about the bacterial species associated with this genus. Here we report the bacterial-associated diversity of P. purpurea in four different localities (Ireland, Italy United Kingdom and the USA) from analyzing eight publicly available metagenomic datasets. These were analyzed with Methaplan3 to identify the putative bacterial taxonomies and their relative abundances. Furthermore, we compared these results to the 16S rRNA metagenomic analysis pipeline of the MGnify database to evaluate both methods. Kraken2 was used to verify and support the results, as a complementary classification method to Metaphlan3. This approach highlighted the different taxonomic resolution of a 16S rRNA OTU-based method compared to the pan-genome approach deployed by Metaphlan3 and complemented by Kraken2. The results presented here provide valuable preliminary data on the putative host-associated bacterial species of P. purpurea.

RevDate: 2021-04-05

Rubio A, AJ Pérez-Pulido (2021)

Protein-Coding Genes of Helicobacter pylori Predominantly Present Purifying Selection though Many Membrane Proteins Suffer from Selection Pressure: A Proposal to Analyze Bacterial Pangenomes.

Genes, 12(3): pii:genes12030377.

The current availability of complete genome sequences has allowed knowing that bacterial genomes can bear genes not present in the genome of all the strains from a specific species. So, the genes shared by all the strains comprise the core of the species, but the pangenome can be much greater and usually includes genes appearing in one only strain. Once the pangenome of a species is estimated, other studies can be undertaken to generate new knowledge, such as the study of the evolutionary selection for protein-coding genes. Most of the genes of a pangenome are expected to be subject to purifying selection that assures the conservation of function, especially those in the core group. However, some genes can be subject to selection pressure, such as genes involved in virulence that need to escape to the host immune system, which is more common in the accessory group of the pangenome. We analyzed 180 strains of Helicobacter pylori, a bacterium that colonizes the gastric mucosa of half the world population and presents a low number of genes (around 1500 in a strain and 3000 in the pangenome). After the estimation of the pangenome, the evolutionary selection for each gene has been calculated, and we found that 85% of them are subject to purifying selection and the remaining genes present some grade of selection pressure. As expected, the latter group is enriched with genes encoding for membrane proteins putatively involved in interaction to host tissues. In addition, this group also presents a high number of uncharacterized genes and genes encoding for putative spurious proteins. It suggests that they could be false positives from the gene finders used for identifying them. All these results propose that this kind of analyses can be useful to validate gene predictions and functionally characterize proteins in complete genomes.

RevDate: 2021-04-01

Jayaram A, Wingate A, Wetterskog D, et al (2021)

Plasma tumor gene conversions after one cycle abiraterone acetate for metastatic castration-resistant prostate cancer: a biomarker analysis of a multi-center international trial.

Annals of oncology : official journal of the European Society for Medical Oncology pii:S0923-7534(21)01074-7 [Epub ahead of print].

BACKGROUND: Plasma tumor DNA fraction is prognostic in metastatic cancers. This could improve risk stratification prior to commencing a new treatment. We hypothesized that a second sample collected after one cycle treatment could refine outcome prediction of patients identified as poor prognosis based on plasma DNA collected pre-treatment.

PATIENTS AND METHODS: Plasma DNA (128 pre-treatment, 134 cycle 2 day 1 (C2D1), and 49 progression) from 151 chemotherapy-naïve metastatic castration resistant prostate cancer (mCRPC) patients in a phase 2 study of abiraterone acetate (NCT01867710) were subjected to custom targeted next-generation sequencing covering exons of these genes:TP53, AR, RB1, PTEN, PIK3CA, BRCA1, BRCA2, ATM, CDK12, CHEK2, FANCA HDAC2, and PALB2. We also captured 1500 pan-genome regions enriched for single nucleotide polymorphisms to allow detection of tumor DNA using the rolling B-allele method. We tested associations with overall survival (OS) and progression-free survival (PFS).

RESULTS: Plasma tumor DNA was associated with shorter OS (hazard ratio (HR): 2.89, 95% confidence intervals (CI): 1.77-4.73, p=<0.0001) and PFS (HR: 2.05; 95% CI: 1.36-3.11, p<0.001). Using a multivariable model, including plasma tumor DNA, patients who had a TP53 or RB1 or PTEN gene alteration pre-treatment and at C2D1 had a significantly shorter OS than patients with no alteration at either time point (TP53, HR 7.13, 95% CI 2.37-21.47, p<0.001; RB1, HR 6.24, 95% CI 1.97-19.73, p=0.002; PTEN, HR 11.9, 95% CI 3.6-39.34, p<0.001). Patients who were positive pre-treatment and converted to undetectable had no evidence of a difference in survival compared to those who were undetectable pre-treatment (respectively p=0.48, p=0.43, p=0.5). Progression samples harbored AR gain in all patients who had gain pre-treatment (9/49) and de novo AR somatic point mutations were detected in 8/49 patients.

CONCLUSIONS: Plasma gene testing after one cycle treatment refines prognostication and could provide an early indication of treatment benefit.

RevDate: 2021-04-01

Barragan AC, D Weigel (2020)

Plant NLR diversity: the known unknowns of pan-NLRomes.

The Plant cell pii:5985533 [Epub ahead of print].

Plants and pathogens constantly adapt to each other. As a consequence, many members of the plant immune system, and especially the intracellular nucleotide-binding site leucine-rich repeat receptors, also known as NOD-like receptors (NLRs), are highly diversified, both among family members in the same genome, and between individuals in the same species. While this diversity has long been appreciated, its true extent has remained unknown. With pan-genome and pan-NLRome studies becoming more and more comprehensive, our knowledge of NLR sequence diversity is growing rapidly, and pan-NLRomes provide powerful platforms for assigning function to NLRs. These efforts are an important step toward the goal of comprehensively predicting from sequence alone whether an NLR provides disease resistance, and if so, to which pathogens.

RevDate: 2021-03-31

Yu D, Banting G, N Neumann (2021)

A Review of the Taxonomy, Genetics and Biology of the Genus Escherichia and the Type Species Escherichia coli.

Canadian journal of microbiology [Epub ahead of print].

Historically, bacteriologists have relied heavily on biochemical and structural phenotypes for bacterial taxonomic classification. However, advances in comparative genomics has led to greater insights into the remarkable genetic diversity within the microbial world, and even within well-accepted species such as Escherichia coli. The extraordinary genetic diversity in E. coli recapitulates the evolutionary radiation of this species in exploiting a wide range of niches (i.e., ecotypes), including the gastrointestinal system of diverse vertebrate hosts as well as non-host natural environments (soil, natural waters, wastewater), which drives the adaptation, natural selection and evolution of intragenotypic conspecific specialism as a strategy for survival. Over the last several years, a growing body of evidence suggests that many E. coli strains appear to be very host (or niche)-specific. While biochemical and phylogenetic evidence support the classification of E. coli as a distinct species, the vast genomic (diverse pan-genome and intragenotypic variability), phenotypic (e.g., metabolic pathways), and ecotypic (host-/niche-specificity) diversity, comparable to the diversity observed in known species complexes, suggests that E. coli is better represented as a complex. Herein we review the taxonomic classification of the genus Escherichia and discuss how phenotype, genotype and ecotype recapitulate our understanding of the biology of this remarkable bacterium.

RevDate: 2021-03-31

Wang M, Fan Y, Liu P, et al (2021)

Genomic insights into evolution of pathogenicity and resistance of multidrug-resistant Raoultella ornithinolytica WM1.

Annals of the New York Academy of Sciences [Epub ahead of print].

Raoultella ornithinolytica is a poorly understood opportunistic pathogen, and the underlying mechanisms of its multidrug resistance and pathogenicity have not yet been comprehensively investigated. The multidrug-resistant (MDR) strain WM1 was isolated from the blood of a male patient in Tianjin, China, in 2018. Here, we describe the complete genome and provide a genomic analysis of R. ornithinolytica WM1. The isolate was resistant to all tested antimicrobials except amikacin, tobramycin, and tigecycline. Two plasmids, pWM1-1 (IncHI5) and pWM1-2 (IncR), carried multidrug-resistance regions. A large antimicrobial resistance island region resided on pWM1-1 and exhibited mosaic structures resulting from the acquisition of complex integrations of variable regions, including genes conferring resistance to multiple classes of antimicrobials. Moreover, WM1 possessed virulence-related elements that encode several virulence factors, including type I fimbriae, Escherichia coli common pilus, type II and VI secretion systems, yersiniabactin, enterobactin, and surface polysaccharide, indicating pathogenic potential. Furthermore, the core genome phylogeny and pan-genome analyses revealed extensive genetic diversity. Our analysis indicates the need for stringent infection control, antimicrobial stewardship, periodic resistance monitoring, and rational medication to address potential threats posed by MDR R. ornithinolytica strains.

RevDate: 2021-03-27

Panthee S, Paudel A, Hamamoto H, et al (2021)

Complete genome sequence and comparative genomic analysis of Enterococcus faecalis EF-2001, a probiotic bacterium.

Genomics pii:S0888-7543(21)00113-0 [Epub ahead of print].

Enterococcus faecalis is a common human gut commensal bacterium. While some E. faecalis strains are probiotic, others are known to cause opportunistic infections, and clear distinction between these strains is difficult using traditional taxonomic approaches. In this study, we completed the genome sequencing of EF-2001, a probiotic strain, using our in-house hybrid assembly approach. Comparative analysis showed that EF-2001 was devoid of cytolysins, major factors associated with pathogenesis, and was phylogenetically distant from pathogenic E. faecalis V583. Genomic analysis of strains with a publicly available complete genome sequence predicted that drug-resistance genes- dfrE, efrA, efrB, emeA, and lsaA were present in all strains, and EF-2001 lacked additional drug-resistance genes. Core- and pan-genome analyses revealed a higher degree of genomic fluidity. We found 49 genes specific to EF-2001, further characterization of which may provide insights into its diverse biological activities. Our comparative genomic analysis approach could help predict the pathogenic or probiotic potential of E. faecalis leading to an early distinction based on genome sequences.

RevDate: 2021-03-26

Kim S, Chung HY, Kwon JG, et al (2021)

Fresh Crab Plays an Important Role as a Nutrient Reservoir for the Rapid Propagation of Vibrio vulnificus.

Frontiers in microbiology, 12:645860.

Vibrio vulnificus is a well-known opportunistic pathogen causing food-borne illnesses by ingestion of contaminated seafood. A new strain of V. vulnificus FORC_016 was isolated from a patient's blood sample in South Korea. The genome consists of two circular DNA chromosomes: chromosome I (3,234,424 bp with a G + C contents of 46.60% containing 2,889 ORFs, 106 tRNA genes, and 31 rRNA genes) and chromosome II (1,837,945 bp with a GC content of 47.00% containing 1,572 ORFs, 13 tRNA genes, and 3 rRNA genes). In addition, chromosome I has a super integron (SI) containing 209 ORFs, which is probably associated with various additional functions including antibiotic resistance and pathogenicity. Pan-genome analysis with other V. vulnificus genomes revealed that core genome regions contain most of the important virulence factors. However, accessory genome regions are located in the SI region and contain unique genes regarding cell wall biosynthesis and generation of host cell protecting capsule, suggesting possible resistance ability against environmental stresses. Comparative RNA-Seq analysis of samples between contact and no contact to the crab conditions showed that expressions of amino acid/peptide and carbohydrate transport and utilization genes were down-regulated, but expressions of cell division and growth-related genes were up-regulated, suggesting that the crab may be a nutrition reservoir for rapid propagation of V. vulnificus. Therefore, consumption of the contaminated fresh crab would provide a large number of V. vulnificus to humans, which may be more dangerous. Consequently, biocontrol of V. vulnificus may be critical to ensure the safety in seafood consumption.

RevDate: 2021-03-24

Hu M, Li C, Xue Y, et al (2021)

Isolation, characterization, and genomic investigation of a phytopathogenic strain of Stenotrophomonas maltophilia.

Phytopathology [Epub ahead of print].

Stenotrophomonas maltophilia is ubiquitous in diverse environmental habitats. It alerts significant concern due to its increasing incidence of nosocomial and community-acquired infection in immunocompromised patients and multiple drug resistance. It is rarely reported as a phytopathogen except causing white stripe disease of rice in India and postharvest fruit rot of Lanzhou Lily. Recently, Dickeya zeae and S. maltophilia strains were simultaneously isolated from soft rot leaves of Clivia miniata in Guangzhou, China, and were both demonstrated pathogenic to the host. Compared with the D. zeae strains, S. maltophilia strains propagated faster for greater growth in LB medium and produced no cellulases or polygalacturonases, more proteases and fewer extracellular polysaccharides. Furthermore, S. maltophilia strains swam and swarmed dramatically less on semi-solid media, but formed extraordinarily more biofilms. Both D. zeae and S. maltophilia strains isolated from clivia caused rot symptoms on other monocot hosts, but not on dicots. Similar to previously reported S. maltophilia strains isolated from other sources, strain JZL8 survived under many antibiotic stresses. Complete genome sequence of S. maltophilia strain JZL8 consists of a chromosome of 4,635,432 bp without plasmid. Pan-genome analysis of JZL8 and 180 other S. maltophilia strains identified 50 JZL8-unique genes, seven of which implicates potential contribution of JZL8 pathogenicity on plants. JZL8 also contains 3 copies of T1SS, likely responsible for its greater production of proteases. Findings from this study extend our knowledge on the host range of S. maltophilia and provide insight into phenotypic and genetic features underlying the plant pathogenicity of JZL8.

RevDate: 2021-03-22

Lorenzi JN, Lespinet O, Leblond P, et al (2021)

Subtelomeres are fast-evolving regions of the Streptomyces linear chromosome.

Microbial genomics [Epub ahead of print].

Streptomyces possess a large linear chromosome (6-12 Mb) consisting of a conserved central region flanked by variable arms covering several megabases. In order to study the evolution of the chromosome across evolutionary times, a representative panel of Streptomyces strains and species (125) whose chromosomes are completely sequenced and assembled was selected. The pan-genome of the genus was modelled and shown to be open with a core-genome reaching 1018 genes. The evolution of Streptomyces chromosome was analysed by carrying out pairwise comparisons, and by monitoring indexes measuring the conservation of genes (presence/absence) and their synteny along the chromosome. Using the phylogenetic depth offered by the chosen panel, it was possible to infer that within the central region of the chromosome, the core-genes form a highly conserved organization, which can reveal the existence of an ancestral chromosomal skeleton. Conversely, the chromosomal arms, enriched in variable genes evolved faster than the central region under the combined effect of rearrangements and addition of new information from horizontal gene transfer. The genes hosted in these regions may be localized there because of the adaptive advantage that their rapid evolution may confer. We speculate that (i) within a bacterial population, the variability of these genes may contribute to the establishment of social characters by the production of 'public goods' (ii) at the evolutionary scale, this variability contributes to the diversification of the genetic pool of the bacteria.

RevDate: 2021-03-20

Zhou X, Zhang XA, Jiang ZW, et al (2021)

Combined characterization of a new member of Marivita cryptomonadis strain LZ-15-2 isolated from cultivable phycosphere microbiota of highly toxic HAB dinoflagellate Alexandrium catenella LZT09.

Brazilian journal of microbiology : [publication of the Brazilian Society for Microbiology] [Epub ahead of print].

During our conveying the microbial structures of phycosphere microbiota (PM) derived from diverse marine harmful algal bloom (HAB) dinoflagellates, a new rod-sharped, white-colored cultivable bacterial strain, designated as LZ-15-2, was isolated from the PM of highly toxic Alexandrium catenella LZT09. Phylogenetic analysis of 16S rRNA gene sequence indicated that strain LZ-15-2 belonged to the genus Marivita within the family Rhodobacteraceae, and demonstrated the highest gene similarity of 99.2% to M. cryptomonadis CL-SK44T, and less than 98.65% with other type strains of Marivita. Phylogenomic calculations on average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the new isolate and M. cryptomonadis CL-SK44T were 99.86% and 99.88%, respectively. Genomic comparison of strain LZ-15-2 with available genomes of Marivita species further verified its taxonomic position within the genus of Marivita. Moreover, comparative genomics analysis showed a proximal similarity of strain LZ-15-2 with M. cryptomonadis CL-SK44T, and it also revealed an open pan-genome status based on constructed gene accumulation curves among Marivita members with 9,361 and 1,712 genes for the pan- and core-genome analysis, respectively. Based on combined polyphasic taxonomic characteristics, strain LZ-15-2 represents a new member of M. cryptomonadis, and proposed as a potential candidate for further exploration of the detailed mechanisms governing the dynamic cross-kingdom algae-bacteria interactions (ABI) between PM and their algal host LZT09.

RevDate: 2021-03-20

Abrouk M, Athiyannan N, Müller T, et al (2021)

Population genomics and haplotype analysis in spelt and bread wheat identifies a gene regulating glume color.

Communications biology, 4(1):375.

The cloning of agriculturally important genes is often complicated by haplotype variation across crop cultivars. Access to pan-genome information greatly facilitates the assessment of structural variations and rapid candidate gene identification. Here, we identified the red glume 1 (Rg-B1) gene using association genetics and haplotype analyses in ten reference grade wheat genomes. Glume color is an important trait to characterize wheat cultivars. Red glumes are frequent among Central European spelt, a dominant wheat subspecies in Europe before the 20th century. We used genotyping-by-sequencing to characterize a global diversity panel of 267 spelt accessions, which provided evidence for two independent introductions of spelt into Europe. A single region at the Rg-B1 locus on chromosome 1BS was associated with glume color in the diversity panel. Haplotype comparisons across ten high-quality wheat genomes revealed a MYB transcription factor as candidate gene. We found extensive haplotype variation across the ten cultivars, with a particular group of MYB alleles that was conserved in red glume wheat cultivars. Genetic mapping and transient infiltration experiments allowed us to validate this particular MYB transcription factor variants. Our study demonstrates the value of multiple high-quality genomes to rapidly resolve copy number and haplotype variations in regions controlling agriculturally important traits.

RevDate: 2021-03-19

Sarjit A, Ravensdale JT, Coorey R, et al (2021)

Survival of Salmonella Under Heat Stress is Associated with the Presence/Absence of CRISPR Cas Genes and Iron Levels.

Current microbiology [Epub ahead of print].

Clustered regularly interspaced short palindromic repeats (CRISPR) cas genes have been linked to stress response in Salmonella. Our aim was to identify the presence of CRISPR cas in Salmonella and its response to heat in the presence of iron. Whole genomes of Salmonella (n = 50) of seven serovars were compared to identify the presence of CRISPR cas genes, direct-repeats and spacers. All Salmonella genomes had all cas genes present except S. Newport 2393 which lacked these genes. Gene-specific primers were used to confirm the absence of these genes in S. Newport 2393. The presence/absence of CRISPR cas genes was further investigated among 469 S. Newport genomes from PATRIC with 283 genomes selected for pan-genome analysis. The response of eleven Salmonella strains of various serovars to gradual heat in ferrous and ferric forms of iron was investigated. A total of 32/283 S. Newport genomes that lacked all CRISPR cas genes clustered together. S. Newport 2393 was the most heat-sensitive strain at higher iron levels (200 and 220 pm) in ferrous and ferric forms of iron. The absence of CRISPR cas genes in S. Newport 2393 may contribute to its increase in heat sensitivity and iron may play a role in this. The high reduction in numbers of most Salmonella strains exposed to heat makes it unfeasible to extract RNA and conduct transcription studies. Further studies should be conducted to validate the survival of Salmonella when exposed to heat in the presence/absence of CRISPR cas genes and different iron levels.

RevDate: 2021-03-19

Lim J, Park HT, Ko S, et al (2021)

Genomic diversity of Mycobacterium avium subsp. paratuberculosis: pangenomic approach for highlighting unique genomic features with newly constructed complete genomes.

Veterinary research, 52(1):46.

Mycobacterium avium subsp. paratuberculosis (MAP) is a causative agent of Johne's disease, which is a chronic granulomatous enteropathy in ruminants. Determining the genetic diversity of MAP is necessary to understand the epidemiology and biology of MAP, as well as establishing disease control strategies. In the present study, whole genome-based alignment and comparative analysis were performed using 40 publicly available MAP genomes, including newly sequenced Korean isolates. First, whole genome-based alignment was employed to identify new genomic structures in MAP genomes. Second, the genomic diversity of the MAP population was described by pangenome analysis. A phylogenetic tree based on the core genome and pangenome showed that the MAP was differentiated into two major types (C- and S-type), which was in keeping with the findings of previous studies. However, B-type strains were discriminated from C-type strains. Finally, functional analysis of the pangenome was performed using three virulence factor databases (i.e., PATRIC, VFDB, and Victors) to predict the phenotypic diversity of MAP in terms of pathogenicity. Based on the results of the pangenome analysis, we developed a real-time PCR technique to distinguish among S-, B- and C-type strains. In conclusion, the results of our study suggest that the phenotypic differences between MAP strains can be explained by their genetic polymorphisms. These results may help to elucidate the diversity of MAP, extending from genomic features to phenotypic traits.

RevDate: 2021-03-17

Edwards RJ, Field MA, Ferguson JM, et al (2021)

Chromosome-length genome assembly and structural variations of the primal Basenji dog (Canis lupus familiaris) genome.

BMC genomics, 22(1):188.

BACKGROUND: Basenjis are considered an ancient dog breed of central African origins that still live and hunt with tribesmen in the African Congo. Nicknamed the barkless dog, Basenjis possess unique phylogeny, geographical origins and traits, making their genome structure of great interest. The increasing number of available canid reference genomes allows us to examine the impact the choice of reference genome makes with regard to reference genome quality and breed relatedness.

RESULTS: Here, we report two high quality de novo Basenji genome assemblies: a female, China (CanFam_Bas), and a male, Wags. We conduct pairwise comparisons and report structural variations between assembled genomes of three dog breeds: Basenji (CanFam_Bas), Boxer (CanFam3.1) and German Shepherd Dog (GSD) (CanFam_GSD). CanFam_Bas is superior to CanFam3.1 in terms of genome contiguity and comparable overall to the high quality CanFam_GSD assembly. By aligning short read data from 58 representative dog breeds to three reference genomes, we demonstrate how the choice of reference genome significantly impacts both read mapping and variant detection.

CONCLUSIONS: The growing number of high-quality canid reference genomes means the choice of reference genome is an increasingly critical decision in subsequent canid variant analyses. The basal position of the Basenji makes it suitable for variant analysis for targeted applications of specific dog breeds. However, we believe more comprehensive analyses across the entire family of canids is more suited to a pangenome approach. Collectively this work highlights the importance the choice of reference genome makes in all variation studies.

RevDate: 2021-03-15

Shirasawa K, Sasaki K, Hirakawa H, et al (2021)

Genomic region associated with pod color variation in pea (Pisum sativum).

G3 (Bethesda, Md.) pii:6171188 [Epub ahead of print].

Pea (Pisum sativum) was chosen as the research material by Gregor Mendel to discover the laws of inheritance. Out of seven traits studied by Mendel, genes controlling three traits including pod shape, pod color, and flower position have not been identified to date. With the aim of identifying the genomic region controlling pod color, we determined the genome sequence of a pea line with yellow pods. Genome sequence reads obtained using a Nanopore sequencing technology were assembled into 117,981 contigs (3.3 Gb), with an N50 value of 51.2 kb. A total of 531,242 potential protein-coding genes were predicted, of which 519,349 (2.8 Gb) were located within repetitive sequences. The assembled sequences were ordered using a reference as a guide to build pseudomolecules. Subsequent genetic and association analyses led to the identification of a genomic region that controls pea pod color. DNA sequences at this genomic location and transcriptome profiles of green and yellow pod lines were analyzed, and genes encoding 3' exoribonucleases were selected as potential candidates controlling pod color. The results presented in this study are expected to accelerate pan-genome studies in pea and facilitate the identification of the gene controlling one of the traits studied by Mendel.w.

RevDate: 2021-03-15

Chen Z, Erickson DL, J Meng (2021)

Polishing the Oxford Nanopore long-read assemblies of bacterial pathogens with Illumina short reads to improve genomic analyses.

Genomics pii:S0888-7543(21)00110-5 [Epub ahead of print].

Oxford Nanopore sequencing has been widely used to achieve complete genomes of bacterial pathogens. However, the error rates of Oxford Nanopore long reads are high. Various polishing algorithms using Illumina short reads to correct the errors in Oxford Nanopore long-read assemblies have been developed. The impact of polishing the Oxford Nanopore long-read assemblies of bacterial pathogens with Illumina short reads on improving genomic analyses was evaluated using both simulated and real reads. Ten species (10 strains) were selected for simulated reads, while real reads were tested on 11 species (11 strains). Oxford Nanopore long reads were assembled with Unicycler to produce a draft assembly, followed by three rounds of polishing with Illumina short reads using two polishing tools, Pilon and NextPolish. One round of NextPolish polishing generated genome completeness and accuracy parameters similar to the reference genomes, whereas two or three rounds of Pilon polishing were needed, though contiguity remained unchanged after polishing. The polished assemblies of Escherichia coli O157:H7, Salmonella Typhimurium, and Cronobacter sakazakii with simulated reads did not provide accurate plasmid identifications. One round of NextPolish polishing was needed for accurately identifying plasmids in Staphylococcus aureus and E. coli O26:H11 with real reads, whereas one and two rounds of Pilon polishing were necessary for these two strains, respectively. Polishing failed to provide an accurate antimicrobial resistance (AMR) genotype for S. aureus with real reads. One round of polishing recovered an accurate AMR genotype for Klebsiella pneumoniae with real reads. The reference genome and draft assembly of Citrobacter braakii with real reads differed, which carried blaCMY-83 and fosA6, respectively, while both genes were present after one round of polishing. However, polishing did not improve the assembly of E. coli O26:H11 with real reads to achieve numbers of virulence genes similar to the reference genome. The draft and polished assemblies showed a phylogenetic tree topology comparable with the reference genomes. For multilocus sequence typing and pan-genome analyses, one round of NextPolish polishing was sufficient to obtain accurate results, while two or three rounds of Pilon polishing were needed. Overall, NextPolish outperformed Pilon for polishing the Oxford Nanopore long-read assemblies of bacterial pathogens, though both polishing strategies improved genomic analyses compared to the draft assemblies.

RevDate: 2021-03-13

Majda S, Beisser D, J Boenigk (2021)

Nutrient-driven genome evolution revealed by comparative genomics of chrysomonad flagellates.

Communications biology, 4(1):328.

Phototrophic eukaryotes have evolved mainly by the primary or secondary uptake of photosynthetic organisms. A return to heterotrophy occurred multiple times in various protistan groups such as Chrysophyceae, despite the expected advantage of autotrophy. It is assumed that the evolutionary shift to mixotrophy and further to heterotrophy is triggered by a differential importance of nutrient and carbon limitation. We sequenced the genomes of 16 chrysophyte strains and compared them in terms of size, function, and sequence characteristics in relation to photo-, mixo- and heterotrophic nutrition. All strains were sequenced with Illumina and partly with PacBio. Heterotrophic taxa have reduced genomes and a higher GC content of up to 59% as compared to phototrophic taxa. Heterotrophs have a large pan genome, but a small core genome, indicating a differential specialization of the distinct lineages. The pan genome of mixotrophs and heterotrophs taken together but not the pan genome of the mixotrophs alone covers the complete functionality of the phototrophic strains indicating a random reduction of genes. The observed ploidy ranges from di- to tetraploidy and was found to be independent of taxonomy or trophic mode. Our results substantiate an evolution driven by nutrient and carbon limitation.

RevDate: 2021-03-12

Mascher M, Wicker T, Jenkins J, et al (2021)

Long-read sequence assembly: a technical evaluation in barley.

The Plant cell pii:6169005 [Epub ahead of print].

Sequence assembly of large and repeat-rich plant genomes has been challenging, requiring substantial computational resources and often several complementary sequence assembly and genome mapping approaches. The recent development of fast and accurate long-read sequencing by circular consensus sequencing (CCS) on the PacBio platform may greatly increase the scope of plant pan-genome projects. Here, we compare current long-read sequencing platforms regarding their ability to rapidly generate contiguous sequence assemblies in pan-genome studies of barley (Hordeum vulgare). Most long-read assemblies are clearly superior to the current barley reference sequence based on short-reads. Assemblies derived from accurate long reads excel in most metrics, but the CCS approach was the most cost-effective strategy for assembling tens of barley genomes. A downsampling analysis indicated that 20-fold CCS coverage can yield very good sequence assemblies, while even 5-fold CCS data may capture the complete sequence of most genes. We present an updated reference genome assembly for barley with near-complete representation of the repeat-rich intergenic space. Long-read assembly can underpin the construction of accurate and complete sequences of multiple genomes of a species to build pan-genome infrastructures in Triticeae crops and their wild relatives.

RevDate: 2021-03-10

Truccollo B, Whyte P, Burgess C, et al (2021)

Genetic characterisation of a subset of Campylobacter jejuni isolates from clinical and poultry sources in Ireland.

PloS one, 16(3):e0246843 pii:PONE-D-20-31624.

Campylobacter spp. is a significant and prevalent public health hazard globally. Campylobacter jejuni is the most frequently recovered species from human cases and poultry are considered the most important reservoir for its transmission to humans. In this study, 30 Campylobacter jejuni isolates were selected from clinical (n = 15) and broiler (n = 15) sources from a larger cohort, based on source, virulence, and antimicrobial resistance profiles. The objective of this study was to further characterise the genomes of these isolates including MLST types, population structure, pan-genome, as well as virulence and antimicrobial resistance determinants. A total of 18 sequence types and 12 clonal complexes were identified. The most common clonal complex was ST-45, which was found in both clinical and broiler samples. We characterised the biological functions that were associated with the core and accessory genomes of the isolates in this study. No significant difference in the prevalence of virulence or antimicrobial resistance determinants was observed between clinical and broiler isolates, although genes associated with severe illness such as neuABC, wlaN and cstIII were only detected in clinical isolates. The ubiquity of virulence factors associated with motility, invasion and cytolethal distending toxin (CDT) synthesis in both clinical and broiler C. jejuni genomes and genetic similarities between groups of broiler and clinical C. jejuni reaffirm that C. jejuni from poultry remains a significant threat to public health.

RevDate: 2021-03-06

Rosselli R, La Porta N, Muresu R, et al (2021)

Pangenomics of the Symbiotic Rhizobiales. Core and Accessory Functions Across a Group Endowed with High Levels of Genomic Plasticity.

Microorganisms, 9(2): pii:microorganisms9020407.

Pangenome analyses reveal major clues on evolutionary instances and critical genome core conservation. The order Rhizobiales encompasses several families with rather disparate ecological attitudes. Among them, Rhizobiaceae, Bradyrhizobiaceae, Phyllobacteriacreae and Xanthobacteriaceae, include members proficient in mutualistic symbioses with plants based on the bacterial conversion of N2 into ammonia (nitrogen-fixation). The pangenome of 12 nitrogen-fixing plant symbionts of the Rhizobiales was analyzed yielding total 37,364 loci, with a core genome constituting 700 genes. The percentage of core genes averaged 10.2% over single genomes, and between 5% to 7% were found to be plasmid-associated. The comparison between a representative reference genome and the core genome subset, showed the core genome highly enriched in genes for macromolecule metabolism, ribosomal constituents and overall translation machinery, while membrane/periplasm-associated genes, and transport domains resulted under-represented. The analysis of protein functions revealed that between 1.7% and 4.9% of core proteins could putatively have different functions.

RevDate: 2021-03-06

Shikov AE, Malovichko YV, Lobov AA, et al (2021)

The Distribution of Several Genomic Virulence Determinants Does Not Corroborate the Established Serotyping Classification of Bacillus thuringiensis.

International journal of molecular sciences, 22(5): pii:ijms22052244.

Bacillus thuringiensis, commonly referred to as Bt, is an object of the lasting interest of microbiologists due to its highly effective insecticidal properties, which make Bt a prominent source of biologicals. To categorize the exuberance of Bt strains discovered, serotyping assays are utilized in which flagellin serves as a primary seroreactive molecule. Despite its convenience, this approach is not indicative of Bt strains' phenotypes, neither it reflects actual phylogenetic relationships within the species. In this respect, comparative genomic and proteomic techniques appear more informative, but their use in Bt strain classification remains limited. In the present work, we used a bottom-up proteomic approach based on fluorescent two-dimensional difference gel electrophoresis (2D-DIGE) coupled with liquid chromatography/tandem mass spectrometry(LC-MS/MS) protein identification to assess which stage of Bt culture, vegetative or spore, would be more informative for strain characterization. To this end, the proteomic differences for the israelensis-attributed strains were assessed to compare sporulating cultures of the virulent derivative to the avirulent one as well as to the vegetative stage virulent bacteria. Using the same approach, virulent spores of the israelensis strain were also compared to the spores of strains belonging to two other major Bt serovars, namely darmstadiensis and thuringiensis. The identified proteins were analyzed regarding the presence of the respective genes in the 104 Bt genome assemblies available at open access with serovar attributions specified. Of 21 proteins identified, 15 were found to be encoded in all the present assemblies at 67% identity threshold, including several virulence factors. Notable, individual phylogenies of these core genes conferred neither the serotyping nor the flagellin-based phylogeny but corroborated the reconstruction based on phylogenomics approaches in terms of tree topology similarity. In its turn, the distribution of accessory protein genes was not confined to the existing serovars. The obtained results indicate that neither gene presence nor the core gene sequence may serve as distinctive bases for the serovar attribution, undermining the notion that the serotyping system reflects strains' phenotypic or genetic similarity. We also provide a set of loci, which fit in with the phylogenomics data plausibly and thus may serve for draft phylogeny estimation of the novel strains.

RevDate: 2021-03-04

Mizzi R, Timms VJ, Price-Carter ML, et al (2021)

Comparative Genomics of Mycobacterium avium Subspecies Paratuberculosis Sheep Strains.

Frontiers in veterinary science, 8:637637.

Mycobacterium avium subspecies paratuberculosis (MAP) is the aetiological agent of Johne's disease (JD), a chronic enteritis that causes major losses to the global livestock industry. Further, it has been associated with human Crohn's disease. Several strains of MAP have been identified, the two major groups being sheep strain MAP, which includes the Type I and Type III sub-lineages, and the cattle strain or Type II MAP lineage, of which bison strains are a sub-grouping. Major genotypic, phenotypic and pathogenic variations have been identified in prior comparisons, but the research has predominately focused on cattle strains of MAP. In countries where the sheep industries are more prevalent, however, such as Australia and New Zealand, ovine JD is a substantial burden. An information gap exists regarding the genomic differences between sheep strain sub-lineages and the relevance of Type I and Type III MAP in terms of epidemiology and/or pathogenicity. We therefore investigated sheep MAP isolates from Australia and New Zealand using whole genome sequencing. For additional context, sheep MAP genome datasets were downloaded from the Sequence Read Archive and GenBank. The final dataset contained 18 Type III and 16 Type I isolates and the K10 cattle strain MAP reference genome. Using a pan-genome approach, an updated global phylogeny for sheep MAP from de novo assemblies was produced. When rooted with the K10 cattle reference strain, two distinct clades representing the lineages were apparent. The Australian and New Zealand isolates formed a distinct sub-clade within the type I lineage, while the European type I isolates formed another less closely related group. Within the type III lineage, isolates appeared more genetically diverse and were from a greater number of continents. Querying of the pan-genome and verification using BLAST analysis revealed lineage-specific variations (n = 13) including genes responsible for metabolism and stress responses. The genetic differences identified may represent important epidemiological and virulence traits specific to sheep MAP. This knowledge will potentially contribute to improved vaccine development and control measures for these strains.

RevDate: 2021-03-03

Kamli MR, Alzahrani NAY, Hajrah NH, et al (2021)

Genome-Driven Discovery of Enzymes with Industrial Implications from the Genus Aneurinibacillus.

Microorganisms, 9(3): pii:microorganisms9030499.

Bacteria belonging to the genus Aneurinibacillus within the family Paenibacillaceae are Gram-positive, endospore-forming, and rod-shaped bacteria inhabiting diverse environments. Currently, there are eight validly described species of Aneurinibacillus; however, several unclassified species have also been reported. Aneurinibacillus spp. have shown the potential for producing secondary metabolites (SMs) and demonstrated diverse types of enzyme activities. These features make them promising candidates with industrial implications. At present, genomes of 9 unique species from the genus Aneurinibacillus are available, which can be utilized to decipher invaluable information on their biosynthetic potential as well as enzyme activities. In this work, we performed the comparative genome analyses of nine Aneurinibacillus species representing the first such comprehensive study of this genus at the genome level. We focused on discovering the biosynthetic, biodegradation, and heavy metal resistance potential of this under-investigated genus. The results indicate that the genomes of Aneurinibacillus contain SM-producing regions with diverse bioactivities, including antimicrobial and antiviral activities. Several carbohydrate-active enzymes (CAZymes) and genes involved in heavy metal resistance were also identified. Additionally, a broad range of enzyme classes were also identified in the Aneurinibacillus pan-genomes, making this group of bacteria potential candidates for future investigations with industrial applications.

RevDate: 2021-03-02

Lugli GA (2021)

Assembly, Annotation, and Comparative Analysis of Bifidobacterial Genomes.

Methods in molecular biology (Clifton, N.J.), 2278:31-44.

Genome assembly and annotation are two of the key actions that must be undertaken in order to explore the genomic repertoire of (bifido)bacteria. The gathered information can be employed to genomically characterize a given microorganism, and can also be used to perform comparative genome analysis by including other sequenced (bifido)bacterial strains. Here, we highlight various bioinformatic programs able to manage next generation sequencing data starting from the assembly of a genome to the comparative analyses between strains.

RevDate: 2021-03-02

Matlock W, Chau KK, AbuOun M, et al (2021)

Genomic network analysis of environmental and livestock F-type plasmid populations.

The ISME journal [Epub ahead of print].

F-type plasmids are diverse and of great clinical significance, often carrying genes conferring antimicrobial resistance (AMR) such as extended-spectrum β-lactamases, particularly in Enterobacterales. Organising this plasmid diversity is challenging, and current knowledge is largely based on plasmids from clinical settings. Here, we present a network community analysis of a large survey of F-type plasmids from environmental (influent, effluent and upstream/downstream waterways surrounding wastewater treatment works) and livestock settings. We use a tractable and scalable methodology to examine the relationship between plasmid metadata and network communities. This reveals how niche (sampling compartment and host genera) partition and shape plasmid diversity. We also perform pangenome-style analyses on network communities. We show that such communities define unique combinations of core genes, with limited overlap. Building plasmid phylogenies based on alignments of these core genes, we demonstrate that plasmid accessory function is closely linked to core gene content. Taken together, our results suggest that stable F-type plasmid backbone structures can persist in environmental settings while allowing dramatic variation in accessory gene content that may be linked to niche adaptation. The association of F-type plasmids with AMR may reflect their suitability for rapid niche adaptation.

RevDate: 2021-03-02

Estrada AA, Gottschalk M, Rendahl A, et al (2021)

Proposed virulence-associated genes of Streptococcus suis isolates from the United States serve as predictors of pathogenicity.

Porcine health management, 7(1):22.

BACKGROUND: There is limited information on the distribution of virulence-associated genes (VAGs) in U.S. Streptococcus suis isolates, resulting in little understanding of the pathogenic potential of these isolates. This lack also reduces our understanding of the epidemiology associated with S. suis in the United States and thus affects the efficiency of control and prevention strategies. In this study we applied whole genome sequencing (WGS)-based approaches for the characterization of S. suis and identification of VAGs.

RESULTS: Of 208 S. suis isolates classified as pathogenic, possibly opportunistic, and commensal pathotypes, the genotype based on the classical VAGs (epf, mrp, and sly encoding the extracellular protein factor, muramidase-release protein, and suilysin, respectively) was identified in 9% (epf+/mrp+/sly+) of the pathogenic pathotype. Using the chi-square test and LASSO regression model, the VAGs ofs (encoding the serum opacity factor) and srtF (encoding sortase F) were selected out of 71 published VAGs as having a significant association with pathotype, and both genes were found in 95% of the pathogenic pathotype. The ofs+/srtF+ genotype was also present in 74% of 'pathogenic' isolates from a separate validation set of isolates. Pan-genome clustering resulted in the differentiation of a group of isolates from five swine production companies into clusters corresponding to clonal complex (CC) and virulence-associated (VA) genotypes. The same CC-VA genotype patterns were identified in multiple production companies, suggesting a lack of association between production company, CC, or VA genotype.

CONCLUSIONS: The proposed ofs and srtF genes were stronger predictors for differentiating pathogenic and commensal S. suis isolates compared to the classical VAGs in two sets of U.S. isolates. Pan-genome analysis in combination with metadata (serotype, ST/CC, VA genotype) was illustrated to be a valuable subtyping tool to describe the genetic diversity of S. suis.

RevDate: 2021-02-25

Louha S, Meinersmann RJ, TC Glenn (2021)

Whole genome genetic variation and linkage disequilibrium in a diverse collection of Listeria monocytogenes isolates.

PloS one, 16(2):e0242297 pii:PONE-D-20-33996.

We performed whole-genome multi-locus sequence typing for 2554 genes in a large and heterogenous panel of 180 Listeria monocytogenes strains having diverse geographical and temporal origins. The subtyping data was used for characterizing genetic variation and evaluating patterns of linkage disequilibrium in the pan-genome of L. monocytogenes. Our analysis revealed the presence of strong linkage disequilibrium in L. monocytogenes, with ~99% of genes showing significant non-random associations with a large majority of other genes in the genome. Twenty-seven loci having lower levels of association with other genes were considered to be potential "hot spots" for horizontal gene transfer (i.e., recombination via conjugation, transduction, and/or transformation). The patterns of linkage disequilibrium in L. monocytogenes suggest limited exchange of foreign genetic material in the genome and can be used as a tool for identifying new recombinant strains. This can help understand processes contributing to the diversification and evolution of this pathogenic bacteria, thereby facilitating development of effective control measures.

RevDate: 2021-02-24

Lawal OU, Fraqueza MJ, Bouchami O, et al (2021)

Foodborne Origin and Local and Global Spread of Staphylococcus saprophyticus Causing Human Urinary Tract Infections.

Emerging infectious diseases, 27(3):880-893.

Staphylococcus saprophyticus is a primary cause of community-acquired urinary tract infections (UTIs) in young women. S. saprophyticus colonizes humans and animals but basic features of its molecular epidemiology are undetermined. We conducted a phylogenomic analysis of 321 S. saprophyticus isolates collected from human UTIs worldwide during 1997-2017 and 232 isolates from human UTIs and the pig-processing chain in a confined region during 2016-2017. We found epidemiologic and genomic evidence that the meat-production chain is a major source of S. saprophyticus causing human UTIs; human microbiota is another possible origin. Pathogenic S. saprophyticus belonged to 2 lineages with distinctive genetic features that are globally and locally disseminated. Pangenome-wide approaches identified a strong association between pathogenicity and antimicrobial resistance, phages, platelet binding proteins, and an increased recombination rate. Our study provides insight into the origin, transmission, and population structure of pathogenic S. saprophyticus and identifies putative new virulence factors.

RevDate: 2021-02-19

Bravo V, Katz A, Porte L, et al (2021)

Genomic analysis of the diversity, antimicrobial resistance and virulence potential of clinical Campylobacter jejuni and Campylobacter coli strains from Chile.

PLoS neglected tropical diseases, 15(2):e0009207 pii:PNTD-D-20-01853 [Epub ahead of print].

Campylobacter jejuni and Campylobacter coli are the leading cause of human gastroenteritis in the industrialized world and an emerging threat in developing countries. The incidence of campylobacteriosis in South America is greatly underestimated, mostly due to the lack of adequate diagnostic methods. Accordingly, there is limited genomic and epidemiological data from this region. In the present study, we performed a genome-wide analysis of the genetic diversity, virulence, and antimicrobial resistance of the largest collection of clinical C. jejuni and C. coli strains from Chile available to date (n = 81), collected in 2017-2019 in Santiago, Chile. This culture collection accounts for more than one third of the available genome sequences from South American clinical strains. cgMLST analysis identified high genetic diversity as well as 13 novel STs and alleles in both C. jejuni and C. coli. Pangenome and virulome analyses showed a differential distribution of virulence factors, including both plasmid and chromosomally encoded T6SSs and T4SSs. Resistome analysis predicted widespread resistance to fluoroquinolones, but low rates of erythromycin resistance. This study provides valuable genomic and epidemiological data and highlights the need for further genomic epidemiology studies in Chile and other South American countries to better understand molecular epidemiology and antimicrobial resistance of this emerging intestinal pathogen.

RevDate: 2021-02-19

Li Y, Sun ZZ, Rong JC, et al (2021)

Comparative genomics reveals broad genetic diversity, extensive recombination and nascent ecological adaptation in Micrococcus luteus.

BMC genomics, 22(1):124.

BACKGROUND: Micrococcus luteus is a group of actinobacteria that is widely used in biotechnology and is being thought as an emerging nosocomial pathogen. With one of the smallest genomes of free-living actinobacteria, it is found in a wide range of environments, but intraspecies genetic diversity and adaptation strategies to various environments remain unclear. Here, comparative genomics, phylogenomics, and genome-wide association studies were used to investigate the genomic diversity, evolutionary history, and the potential ecological differentiation of the species.

RESULTS: High-quality genomes of 66 M. luteus strains were downloaded from the NCBI GenBank database and core and pan-genome analysis revealed a considerable intraspecies heterogeneity. Phylogenomic analysis, gene content comparison, and average nucleotide identity calculation consistently indicated that the species has diverged into three well-differentiated clades. Population structure analysis further suggested the existence of an unknown ancestor or the fourth, yet unsampled, clade. Reconstruction of gene gain/loss events along the evolutionary history revealed both early events that contributed to the inter-clade divergence and recent events leading to the intra-clade diversity. We also found convincing evidence that recombination has played a key role in the evolutionary process of the species, with upto two-thirds of the core genes having been affected by recombination. Furthermore, distribution of mammal-associated strains (including pathogens) on the phylogenetic tree suggested that the last common ancestor had a free-living lifestyle, and a few recently diverged lineages have developed a mammal-associated lifestyle separately. Consistently, genome-wide association analysis revealed that mammal-associated strains from different lineages shared genes functionally relevant to the host-associated lifestyle, indicating a recent ecological adaption to the new host-associated habitats.

CONCLUSIONS: These results revealed high intraspecies genomic diversity of M. luteus and highlighted that gene gain/loss events and extensive recombination events played key roles in the genome evolution. Our study also indicated that, as a free-living species, some lineages have recently developed or are developing a mammal-associated lifestyle. This study provides insights into the mechanisms that drive the genome evolution and adaption to various environments of a bacterial species.

RevDate: 2021-02-16

Aguirre-Sanchez JR, Ibarra-Rodriguez JR, Vega-Lopez IF, et al (2021)

Genomic signatures of adaptation to natural settings in non-typhoidal Salmonella enterica Serovars Saintpaul, Thompson and Weltevreden.

Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases pii:S1567-1348(21)00068-X [Epub ahead of print].

Salmonella enterica is a pathogenic bacterium responsible for intestinal illness and systemic diseases such as typhoid and paratyphoid fevers. Among clinical manifestation classification, non-typhoidal Salmonella is mainly known as foodborne pathogen associated with the consumption of fecal contaminated food and water. Even though Salmonella hosts include humans and warm-blooded animals, it has been found in non-host environments as river water where the bacteria use different strategies to fitness the environment persisting and establishment. Now with the availability of WGS and bioinformatics tools, we can explore bacterial genomes with higher resolution to increase our understanding of specific genetic signatures among environmental and clinical isolates, being the goal of this work. Pangenome construction allowed the detection of specific environmental and clinical gene clusters related to metabolism and secretion systems as the main signature respectively. Specifically, D-galactonate degradation pathway was observed mainly in environmental genomes while T3SS and flagellum genes were detected for all clinical but not for all environmental isolates. Gene duplication and pseudogenes accumulation were detected as the main adaptation strategy for environmental isolates; thus, isolation source may play an important role in genome plasticity, conferring a selective advantage to survive and persist for environmental Salmonella isolates. Intact prophage sequences with cargo genes were observable for both isolation sources playing an important role in virulence contribution.

RevDate: 2021-02-15

Gutiérrez S, Díaz L, Reyes-Jara A, et al (2020)

Whole-Genome Phylogenetic Analysis Reveals a Wide Diversity of Non-O157 STEC Isolated From Ground Beef and Cattle Feces.

Frontiers in microbiology, 11:622663.

Shiga toxin-producing Escherichia coli (STEC) causes foodborne outbreaks that can lead to complications such as hemolytic uremic syndrome. Their main reservoir is cattle, and ground beef has been frequently associated with disease and outbreaks. In this study, we attempted to understand the genetic relationship among STEC isolated in Chile from different sources, their relationship to STEC from the rest of the world, and to identify molecular markers of Chilean STEC. We sequenced 62 STEC isolated in Chile using MiSeq Illumina. In silico typing was determined using tools of the Center Genomic Epidemiology, Denmark University (CGE/DTU). Genomes of our local STEC collection were compared with 113 STEC isolated worldwide through a core genome MLST (cgMLST) approach, and we also searched for distinct genes to be used as molecular markers of Chilean isolates. Genomes in our local collection were grouped based on serogroup and sequence type, and clusters were formed within local STEC. In the worldwide STEC analysis, Chilean STEC did not cluster with genomes of the rest of the world suggesting that they are not phylogenetically related to previously described STEC. The pangenome of our STEC collection was 11,650 genes, but we did not identify distinct molecular markers of local STEC. Our results showed that there may be local emerging STEC with unique features, nevertheless, no molecular markers were detected. Therefore, there might be elements such as a syntenic organization that might explain differential clustering detected between local and worldwide STEC.

RevDate: 2021-02-14

Thukral A, Ross K, Hansen C, et al (2020)

A single dose polyanhydride-based nanovaccine against paratuberculosis infection.

NPJ vaccines, 5(1):15.

Mycobacterium avium subsp. paratuberculosis (M. paratuberculosis) causes Johne's disease in ruminants and is characterized by chronic gastroenteritis leading to heavy economic losses to the dairy industry worldwide. The currently available vaccine (inactivated bacterin in oil base) is not effective in preventing pathogen shedding and is rarely used to control Johne's disease in dairy herds. To develop a better vaccine that can prevent the spread of Johne's disease, we utilized polyanhydride nanoparticles (PAN) to encapsulate mycobacterial antigens composed of whole cell lysate (PAN-Lysate) and culture filtrate (PAN-Cf) of M. paratuberculosis. These nanoparticle-based vaccines (i.e., nanovaccines) were well tolerated in mice causing no inflammatory lesions at the site of injection. Immunological assays demonstrated a substantial increase in the levels of antigen-specific T cell responses post-vaccination in the PAN-Cf vaccinated group as indicated by high percentages of triple cytokine (IFN-γ, IL-2, TNF-α) producing CD8+ T cells. Following challenge, animals vaccinated with PAN-Cf continued to produce significant levels of double (IFN-γ, TNF-α) and single cytokine (IFN-γ) secreting CD8+ T cells compared with animals vaccinated with an inactivated vaccine. A significant reduction in bacterial load was observed in multiple organs of animals vaccinated with PAN-Cf, which is a clear indication of protection. Overall, the use of polyanhydride nanovaccines resulted in development of protective and sustained immunity against Johne's disease, an approach that could be applied to counter other intracellular pathogens.

RevDate: 2021-02-13

Perrin A, EPC Rocha (2021)

PanACoTA: a modular tool for massive microbial comparative genomics.

NAR genomics and bioinformatics, 3(1):lqaa106.

The study of the gene repertoires of microbial species, their pangenomes, has become a key part of microbial evolution and functional genomics. Yet, the increasing number of genomes available complicates the establishment of the basic building blocks of comparative genomics. Here, we present PanACoTA (https://github.com/gem-pasteur/PanACoTA), a tool that allows to download all genomes of a species, build a database with those passing quality and redundancy controls, uniformly annotate and then build their pangenome, several variants of core genomes, their alignments and a rapid but accurate phylogenetic tree. While many programs building pangenomes have become available in the last few years, we have focused on a modular method, that tackles all the key steps of the process, from download to phylogenetic inference. While all steps are integrated, they can also be run separately and multiple times to allow rapid and extensive exploration of the parameters of interest. PanACoTA is built in Python3, includes a singularity container and features to facilitate its future development. We believe PanACoTa is an interesting addition to the current set of comparative genomics tools, since it will accelerate and standardize the more routine parts of the work, allowing microbial genomicists to more quickly tackle their specific questions.

RevDate: 2021-02-12

Lin YT, Lee CC, Leu WM, et al (2021)

Fungicidal Activity of Volatile Organic Compounds Emitted by Burkholderia gladioli Strain BBB-01.

Molecules (Basel, Switzerland), 26(3): pii:molecules26030745.

A Burkholderia gladioli strain, named BBB-01, was isolated from rice shoots based on the confrontation plate assay activity against several plant pathogenic fungi. The genome of this bacterial strain consists of two circular chromosomes and one plasmid with 8,201,484 base pairs in total. Pangenome analysis of 23 B. gladioli strains suggests that B. gladioli BBB-01 has the closest evolutionary relationship to B. gladioli pv. gladioli and B. gladioli pv. agaricicola. B. gladioli BBB-01 emitted dimethyl disulfide and 2,5-dimethylfuran when it was cultivated in lysogeny broth and potato dextrose broth, respectively. Dimethyl disulfide is a well-known pesticide, while the bioactivity of 2,5-dimethylfuran has not been reported. In this study, the inhibition activity of the vapor of these two compounds was examined against phytopathogenic fungi, including Magnaporthe oryzae, Gibberella fujikuroi, Sarocladium oryzae, Phellinus noxius and Colletotrichumfructicola, and human pathogen Candida albicans. In general, 2,5-dimethylfuran is more potent than dimethyl disulfide in suppressing the growth of the tested fungi, suggesting that 2,5-dimethylfuran is a potential fumigant to control plant fungal disease.

RevDate: 2021-02-12

Chen X, Li R, Wang Y, et al (2021)

Genomic Characterization Provides an Insight into the Pathogenicity of the Poplar Canker Bacterium Lonsdalea populi.

Genes, 12(2): pii:genes12020246.

An emerging poplar canker caused by the gram-negative bacterium, Lonsdalea populi, has led to high mortality of hybrid poplars Populus × euramericana in China and Europe. The molecular bases of pathogenicity and bark adaptation of L. populi have become a focus of recent research. This study revealed the whole genome sequence and identified putative virulence factors of L. populi. A high-quality L. populi genome sequence was assembled de novo, with a genome size of 3,859,707 bp, containing approximately 3434 genes and 107 RNAs (75 tRNA, 22 rRNA, and 10 ncRNA). The L. populi genome contained 380 virulence-associated genes, mainly encoding for adhesion, extracellular enzymes, secretory systems, and two-component transduction systems. The genome had 110 carbohydrate-active enzyme (CAZy)-coding genes and putative secreted proteins. The antibiotic-resistance database annotation listed that L. populi was resistant to penicillin, fluoroquinolone, and kasugamycin. Analysis of comparative genomics found that L. populi exhibited the highest homology with the L. britannica genome and L. populi encompassed 1905 specific genes, 1769 dispensable genes, and 1381 conserved genes, suggesting high evolutionary diversity and genomic plasticity. Moreover, the pan genome analysis revealed that the N-5-1 genome is an open genome. These findings provide important resources for understanding the molecular basis of the pathogenicity and biology of L. populi and the poplar-bacterium interaction.

RevDate: 2021-02-11

Mao B, Yin R, Li X, et al (2021)

Comparative Genomic Analysis of Lactiplantibacillus plantarum Isolated from Different Niches.

Genes, 12(2): pii:genes12020241.

Lactiplantibacillus plantarum can adapt to a variety of niches and is widely distributed in many sources. We used comparative genomics to explore the differences in the genome and in the physiological characteristics of L. plantarum isolated from pickles, fermented sauce, and human feces. The relationships between genotypes and phenotypes were analyzed to address the effects of isolation source on the genetic variation of L. plantarum. The comparative genomic results indicate that the numbers of unique genes in the different strains were niche-dependent. L. plantarum isolated from fecal sources generally had more strain-specific genes than L. plantarum isolated from pickles. The phylogenetic tree and average nucleotide identity (ANI) results indicate that L. plantarum in pickles and fermented sauce clustered independently, whereas the fecal L. plantarum was distributed more uniformly in the phylogenetic tree. The pan-genome curve indicated that the L. plantarum exhibited high genomic diversity. Based on the analysis of the carbohydrate active enzyme and carbohydrate-use abilities, we found that L. plantarum strains isolated from different sources exhibited different expression of the Glycoside Hydrolases (GH) and Glycosyl Transferases (GT) families and that the expression patterns of carbohydrate active enzymes were consistent with the evolution relationships of the strains. L. plantarum strains exhibited niche-specific characteristicsand the results provided better understating on genetics of this species.

RevDate: 2021-02-10

Yamaguchi M, Win HPM, Higashi K, et al (2021)

Epidemiological analysis of pneumococcal strains isolated at Yangon Children's Hospital in Myanmar via whole-genome sequencing-based methods.

Microbial genomics [Epub ahead of print].

Streptococcus pneumoniae causes over one million deaths from lower respiratory infections per annum worldwide. Although mortality is very high in Southeast Asian countries, molecular epidemiological information remains unavailable for some countries. In this study, we report, for the first time, the whole-genome sequences and genetic profiles of pneumococcal strains isolated in Myanmar. We isolated 60 streptococcal strains from 300 children with acute respiratory infection at Yangon Children's Hospital in Myanmar. We obtained whole-genome sequences and identified the species, serotypes, sequence types, antimicrobial resistance (AMR) profiles, virulence factor profiles and pangenome structure using sequencing-based analysis. Average nucleotide identity analysis indicated that 58 strains were S. pneumoniae and the other 2 strains were Streptococcus mitis. The major serotype was 19F (11 strains), followed by 6E (6B genetic variant; 7 strains) and 15 other serotypes; 5 untypable strains were also detected. Multilocus sequence typing analysis revealed 39 different sequence types, including 11 novel ones. In addition, genetic profiling indicated that AMR genes and mutations spread among pneumococcal strains in Myanmar. A minimum inhibitory concentration assay indicated that several pneumococcal strains had acquired azithromycin and tetracycline resistance, whereas no strains were found to be resistant against levofloxacin and high-dose penicillin G. Phylogenetic and pangenome analysis showed various pneumococcal lineages and that the pneumococcal strains contain a rich and mobile gene pool, providing them with the ability to adapt to selective pressures. This molecular epidemiological information can help in tracking global infection and supporting AMR control in addition to public health interventions in Myanmar.

RevDate: 2021-02-10

Yocca AE, Lu Z, Schmitz RJ, et al (2021)

Evolution of conserved noncoding sequences in Arabidopsis thaliana.

Molecular biology and evolution pii:6132240 [Epub ahead of print].

Recent pangenome studies have revealed a large fraction of the gene content within a species exhibits presence-absence variation (PAV). However, coding regions alone provide an incomplete assessment of functional genomic sequence variation at the species level. Little to no attention has been paid to noncoding regulatory regions in pangenome studies, though these sequences directly modulate gene expression and phenotype. To uncover regulatory genetic variation, we generated chromosome-scale genome assemblies for thirty Arabidopsis thaliana accessions from multiple distinct habitats and characterized species level variation in Conserved Noncoding Sequences (CNS). Our analyses uncovered not only PAV and positional variation (PosV) but that diversity in CNS is non-random, with variants shared across different accessions. Using evolutionary analyses and chromatin accessibility data, we provide further evidence supporting roles for conserved and variable CNS in gene regulation. Additionally, our data suggests transposable elements contribute to CNS variation. Characterizing species-level diversity in all functional genomic sequences may later uncover previously unknown mechanistic links between genotype and phenotype.

RevDate: 2021-02-13

Grazziotin AL, Vidal NM, Hoepers PG, et al (2021)

Comparative genomics of a novel clade shed light on the evolution of the genus Erysipelothrix and characterise an emerging species.

Scientific reports, 11(1):3383.

Erysipelothrix sp. isolates obtained from a deadly outbreak in farmed turkeys were sequenced and compared to representatives of the genus. Phylogenetic trees-supported by digital DNA:DNA hybridization and Average Nucleotide Identity-revealed a novel monophyletic clade comprising isolates from pigs, turkeys, and fish, including isolates previously described as E. sp. Strain 2. Genes coding for the SpaC protein, typically found in E. sp. Strain 2, were detected in all isolates of the clade. Therefore, we confirm E. sp. Strain 2 represents a unique species that may be isolated from a broad host range, and the name "Erysipelothrix takahashiae" is suggested. Core genome analysis showed that the pathogenic species of this genus, E. rhusiopathiae and the clade E. sp. Strain 2, are enriched in core functionalities related to nutrient uptake and transport, but not necessarily homologous pathways. For instance, whereas the aerobic DctA transporter may uptake C4-dicarboxylates in both species, the anaerobic DcuC transporter is exclusive of the E. sp. Strain 2. Remarkably, the pan-genome analysis uncovered that genes related to transport and metabolism, recombination and repair, translation and transcription in the fish isolate, within the novel clade, have undergone a genomic reduction through pseudogenization. This reflects distinct selective pressures shaping the genome of species and strains within the genus Erysipelothrix while adapting to their respective niches.

RevDate: 2021-02-13

Costa D, Lévesque S, Kumar N, et al (2021)

Pangenome analysis reveals genetic isolation in Campylobacter hyointestinalis subspecies adapted to different mammalian hosts.

Scientific reports, 11(1):3431.

Campylobacter hyointestinalis is an emerging pathogen currently divided in two subspecies: C. hyointestinalis subsp. lawsonii which is predominantly recovered from pigs, and C. hyointestinalis subsp. hyointestinalis which can be found in a much wider range of mammalian hosts. Despite C. hyointestinalis being reported as an emerging pathogen, its evolutionary and host-associated diversification patterns are still vastly unexplored. For this reason, we generated whole-genome sequences of 13 C. hyointestinalis subsp. hyointestinalis strains and performed a comprehensive comparative analysis including publicly available C. hyointestinalis subsp. hyointestinalis and C. hyointestinalis subsp. lawsonii genomes, to gain insight into the genomic variation of these differentially-adapted subspecies. Both subspecies are distinct phylogenetic lineages which present an apparent barrier to homologous recombination, suggesting genetic isolation. This is further supported by accessory gene patterns that recapitulate the core genome phylogeny. Additionally, C. hyointestinalis subsp. hyointestinalis presents a bigger and more diverse accessory genome, which probably reflects its capacity to colonize different mammalian hosts unlike C. hyointestinalis subsp. lawsonii that is presumably host-restricted. This greater plasticity in the accessory genome of C. hyointestinalis subsp. hyointestinalis correlates to a higher incidence of genome-wide recombination events, that may be the underlying mechanism driving its diversification. Concordantly, both subspecies present distinct patterns of gene families involved in genome plasticity and DNA repair like CRISPR-associated proteins and restriction-modification systems. Together, our results provide an overview of the genetic mechanisms shaping the genomes of C. hyointestinalis subspecies, contributing to understand the biology of Campylobacter species that are increasingly recognized as emerging pathogens.

RevDate: 2021-02-13

Sielemann K, Weisshaar B, B Pucker (2021)

Reference-based QUantification Of gene Dispensability (QUOD).

Plant methods, 17(1):18.

BACKGROUND: Dispensability of genes in a phylogenetic lineage, e.g. a species, genus, or higher-level clade, is gaining relevance as most genome sequencing projects move to a pangenome level. Most analyses classify genes as core genes, which are present in all investigated individual genomes, and dispensable genes, which only occur in a single or a few investigated genomes. The binary classification as 'core' or 'dispensable' is often based on arbitrary cutoffs of presence/absence in the analysed genomes. Even when extended to 'conditionally dispensable', this concept still requires the assignment of genes to distinct groups.

RESULTS: Here, we present a new method which overcomes this distinct classification by quantifying gene dispensability and present a dedicated tool for reference-based QUantification Of gene Dispensability (QUOD). As a proof of concept, sequence data of 966 Arabidopsis thaliana accessions (Ath-966) were processed to calculate a gene-specific dispensability score for each gene based on normalised coverage in read mappings. We validated this score by comparison of highly conserved Benchmarking Universal Single Copy Orthologs (BUSCOs) to all other genes. The average scores of BUSCOs were significantly lower than the scores of non-BUSCOs. Analysis of variation demonstrated lower variation values between replicates of a single accession than between iteratively, randomly selected accessions from the whole dataset Ath-966. Functional investigations revealed defense and antimicrobial response genes among the genes with high-dispensability scores.

CONCLUSIONS: Instead of classifying a gene as core or dispensable, QUOD assigns a dispensability score to each gene. Hence, QUOD facilitates the identification of candidate dispensable genes, associated with high dispensability scores, which often underlie lineage-specific adaptation to varying environmental conditions.

RevDate: 2021-02-13

Sela I, Wolf YI, EV Koonin (2021)

Assessment of assumptions underlying models of prokaryotic pangenome evolution.

BMC biology, 19(1):27.

BACKGROUND: The genomes of bacteria and archaea evolve by extensive loss and gain of genes which, for any group of related prokaryotic genomes, result in the formation of a pangenome with the universal, asymmetrical U-shaped distribution of gene commonality. However, the evolutionary factors that define the specific shape of this distribution are not thoroughly understood.

RESULTS: We investigate the fit of simple models of genome evolution to the empirically observed gene commonality distributions and genome intersections for 33 groups of closely related bacterial genomes. A model with an infinite external gene pool available for gene acquisition and constant genome size (IGP-CGS model), and two gene turnover rates, one for slow- and the other one for fast-evolving genes, allows two approaches to estimate the parameters for gene content dynamics. One is by fitting the model prediction to the distribution of the number of genes shared by precisely k genomes (gene commonality distribution) and another by analyzing the distribution of the number of genes common for k genome sets (k-cores). Both approaches produce a comparable overall quality of fit, although the former significantly overestimates the number of the universally conserved genes, while the latter overestimates the number of singletons. We further explore the effect of dropping each of the assumptions of the IGP-CGS model on the fit to the gene commonality distributions and show that models with either a finite gene pool or unequal rates of gene loss and gain (greater gene loss rate) eliminate the overestimate of the number of singletons or the core genome size.

CONCLUSIONS: We examine the assumptions that are usually adopted for modeling the evolution of the U-shaped gene commonality distributions in prokaryote genomes, namely, those of infinitely many genes and constant genome size. The combined analysis of genome intersections and gene commonality suggests that at least one of these assumptions is invalid. The violation of both these assumptions reflects the limited ability of prokaryotes to gain new genes. This limitation seems to stem, at least partly, from the horizontal gene transfer barrier, i.e., the cost of accommodation of foreign genes by prokaryotes. Further development of models taking into account the complexity of microbial evolution is necessary for an improved understanding of the evolution of prokaryotes.

RevDate: 2021-02-13

Maeno S, Nishimura H, Tanizawa Y, et al (2021)

Unique niche-specific adaptation of fructophilic lactic acid bacteria and proposal of three Apilactobacillus species as novel members of the group.

BMC microbiology, 21(1):41.

BACKGROUND: Fructophilic lactic acid bacteria (FLAB) found in D-fructose rich niches prefer D-fructose over D-glucose as a growth substrate. They need electron acceptors for growth on D-glucose. The organisms share carbohydrate metabolic properties. Fructobacillus spp., Apilactobacillus kunkeei, and Apilactobacillus apinorum are members of this unique group. Here we studied the fructophilic characteristics of recently described species Apilactobacillus micheneri, Apilactobacillus quenuiae, and Apilactobacillus timberlakei.

RESULTS: The three species prefer D-fructose over D-glucose and only metabolize D-glucose in the presence of electron acceptors. The genomic characteristics of the three species, i.e. small genomes and thus a low number of coding DNA sequences, few genes involved in carbohydrate transport and metabolism, and partial deletion of adhE gene, are characteristic of FLAB. The three species thus are novel members of FLAB. Reduction of genes involved in carbohydrate transport and metabolism in accordance with reduction of genome size were the common characteristics of the family Lactobacillaceae, but FLAB markedly reduced the gene numbers more than other species in the family. Pan-genome analysis of genes involved in metabolism displayed a lack of specific carbohydrate metabolic pathways in FLAB, leading to a unique cluster separation.

CONCLUSIONS: The present study expanded FLAB group. Fructose-rich environments have induced similar evolution in phylogenetically distant FLAB species. These are examples of convergent evolution of LAB.

RevDate: 2021-02-10

Chandrasekar SS, Phanse Y, Hildebrand RE, et al (2021)

Localized and Systemic Immune Responses against SARS-CoV-2 Following Mucosal Immunization.

Vaccines, 9(2): pii:vaccines9020132.

The rapid transmission of SARS-CoV-2 in the USA and worldwide necessitates the development of multiple vaccines to combat the COVID-19 global pandemic. Previously, we showed that a particulate adjuvant system, quil-A-loaded chitosan (QAC) nanoparticles, can elicit robust immunity combined with plasmid vaccines when used against avian coronavirus. Here, we report on the immune responses elicited by mucosal homologous plasmid and a heterologous immunization strategy using a plasmid vaccine and a Modified Vaccinia Ankara (MVA) expressing SARS-CoV-2 spike (S) and nucleocapsid (N) antigens. Only the heterologous intranasal immunization strategy elicited neutralizing antibodies against SARS-CoV-2 in serum and bronchoalveolar lavage of mice, suggesting a protective vaccine. The same prime/boost strategy led to the induction of type 1 and type 17 T-cell responses and polyfunctional T-cells expressing multiple type 1 cytokines (e.g., IFN-γ, TNFα, IL-2) in the lungs and spleens of vaccinated mice. In contrast, the plasmid homologous vaccine strategy led to the induction of local mono and polyfunctional T-cells secreting IFN-γ. Outcomes of this study support the potential of QAC-nano vaccines to elicit significant mucosal immune responses against respiratory coronaviruses.

RevDate: 2021-02-05

Koonin EV, Makarova KS, YI Wolf (2021)

Evolution of Microbial Genomics: Conceptual Shifts over a Quarter Century.

Trends in microbiology pii:S0966-842X(21)00007-X [Epub ahead of print].

Prokaryote genomics started in earnest in 1995, with the complete sequences of two small bacterial genomes, those of Haemophilus influenzae and Mycoplasma genitalium. During the next quarter century, the prokaryote genome database has been growing exponentially, with no saturation in sight. For most of these 25 years, genome sequencing remained limited to cultivable microbes. Together with next-generation sequencing methods, advances in metagenomics and single-cell genomics have lifted this limitation, providing for an increasingly unbiased characterization of the global prokaryote diversity. Advances in computational genomics followed the progress of genome sequencing, even if occasionally lagging behind. Several major new branches of bacteria and archaea were discovered, including Asgard archaea, the apparent closest relatives of eukaryotes and expansive groups of bacteria and archaea with small genomes thought to be symbionts of other prokaryotes. Comparative analysis of numerous prokaryote genomes spanning a wide range of evolutionary distances changed the conceptual foundations of microbiology, supplanting the notion of species genomes with fixed gene sets with that of dynamic pangenomes and the notion of a single Tree of Life (ToL) with a statistical tree-like trend among individual gene trees. Strides were also made towards a theory and quantitative laws of prokaryote genome evolution.

RevDate: 2021-02-13

Mageiros L, Méric G, Bayliss SC, et al (2021)

Genome evolution and the emergence of pathogenicity in avian Escherichia coli.

Nature communications, 12(1):765.

Chickens are the most common birds on Earth and colibacillosis is among the most common diseases affecting them. This major threat to animal welfare and safe sustainable food production is difficult to combat because the etiological agent, avian pathogenic Escherichia coli (APEC), emerges from ubiquitous commensal gut bacteria, with no single virulence gene present in all disease-causing isolates. Here, we address the underlying evolutionary mechanisms of extraintestinal spread and systemic infection in poultry. Combining population scale comparative genomics and pangenome-wide association studies, we compare E. coli from commensal carriage and systemic infections. We identify phylogroup-specific and species-wide genetic elements that are enriched in APEC, including pathogenicity-associated variation in 143 genes that have diverse functions, including genes involved in metabolism, lipopolysaccharide synthesis, heat shock response, antimicrobial resistance and toxicity. We find that horizontal gene transfer spreads pathogenicity elements, allowing divergent clones to cause infection. Finally, a Random Forest model prediction of disease status (carriage vs. disease) identifies pathogenic strains in the emergent ST-117 poultry-associated lineage with 73% accuracy, demonstrating the potential for early identification of emergent APEC in healthy flocks.

RevDate: 2021-02-03

Glick L, I Mayrose (2021)

Panoramic: A package for constructing eukaryotic pan-genomes.

Molecular ecology resources [Epub ahead of print].

The study of intraspecific genomic variation in eukaryotic species has been the focus of numerous genome resequencing projects in recent years. One emerging approach for the analysis of intraspecific diversity uses the concept of a pan-genome, which theoretically represents the full set of genomic sequences and coding genes from all individuals of a given species. This approach has many advantages over reference-based methods and has been successfully applied to study both prokaryotic and eukaryotic species. However, the process of pan-genome construction still presents considerable scientific and technical challenges, especially for eukaryotic species with large and complex genomes. Although general approaches for the construction of pan-genomes have been devised, currently available software tools implement only certain modules of the entire computational procedure. Therefore, each pan-genome project requires the development of tailored analysis pipelines, thus complicating and prolonging the process and impairing research reproducibility and comparison across studies. Here we present Panoramic, a software package for the automatic construction of eukaryotic pan-genomes. Panoramic takes raw sequencing reads as input and applies two alternative approaches for pan-genome construction. Panoramic makes pan-genome construction a considerably easier task by providing simple user interface and efficient data processing algorithms. We demonstrate the use of Panoramic by constructing the pan-genome of the model plant species Arabidopsis thaliana from sequencing data of 20 diverse ecotypes.

RevDate: 2021-02-03

Schulz T, Wittler R, Rahmann S, et al (2021)

Detecting High Scoring Local Alignments in Pangenome Graphs.

Bioinformatics (Oxford, England) pii:6126799 [Epub ahead of print].

MOTIVATION: Increasing amounts of individual genomes sequenced per species motivate the usage of pangenomic approaches. Pangenomes may be represented as graphical structures, e.g. compacted colored de Bruijn graphs, which offer a low memory usage and facilitate reference-free sequence comparisons. While sequence-to-graph mapping to graphical pangenomes has been studied for some time, no local alignment search tool in the vein of BLAST has been proposed yet.

RESULTS: We present a new heuristic method to find maximum scoring local alignments of a DNA query sequence to a pangenome represented as a compacted colored de Bruijn graph. Our approach additionally allows a comparison of similarity among sequences within the pangenome. We show that local alignment scores follow an exponential-tail distribution similar to BLAST scores, and we discuss how to estimate its parameters to separate local alignments representing sequence homology from spurious findings. An implementation of our method is presented, and its performance and usability are shown. Our approach scales sublinearly in running time and memory usage with respect to the number of genomes under consideration. This is an advantage over classical methods that do not make use of sequence similarity within the pangenome.

AVAILABILITY: Source code and test data are available from https://gitlab.ub.uni-bielefeld.de/gi/plast.

SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

RevDate: 2021-02-08

Suryaletha K, Chandrika SK, S Thomas (2021)

Comprehensive genomics depict accessory genes encoding pathogenicity and biofilm determinants in Enterococcus faecalis.

Future microbiology, 16:175-184.

Aim:Enterococcus faecalis is a leading nosocomial pathogen in biofilm-associated polymicrobial infections. The study aims to understand pathogenicity and biofilm determinants of the pathogen by genome analysis. Methodology: Genome sequencing of a strong biofilm forming clinical isolate Enterococcus faecalis SK460 devoid of Fsr quorum-signaling system, was performed and comparative genomics was carried out among a set of pathogenic biofilm formers and nonpathogenic weak biofilm formers. Results: Analysis revealed a pool of virulence and adhesion related factors associated with pathogenicity. Absence of CRISPR-Cas system facilitated acquisition of pheromone responsive plasmid, pathogenicity island and phages. Comprehensive analysis identified a subset of accessory genes encoding polysaccharide lyase, sugar phosphotransferase system, phage proteins and transcriptional regulators exclusively in pathogenic biofilm formers. Conclusion: The study identified a set of genes specific to pathogenic biofilm formers and these can act as targets which in turn help to develop future treatment endeavors against enterococcal infections.

RevDate: 2021-02-11

Przewieslik-Allen AM, Wilkinson PA, Burridge AJ, et al (2021)

The role of gene flow and chromosomal instability in shaping the bread wheat genome.

Nature plants [Epub ahead of print].

Bread wheat (Triticum aestivum) is one of the world's most important crops; however, a low level of genetic diversity within commercial breeding accessions can significantly limit breeding potential. In contrast, wheat relatives exhibit considerable genetic variation and so potentially provide a valuable source of novel alleles for use in breeding new cultivars. Historically, gene flow between wheat and its relatives may have contributed novel alleles to the bread wheat pangenome. To assess the contribution made by wheat relatives to genetic diversity in bread wheat, we used markers based on single nucleotide polymorphisms to compare bread wheat accessions, created in the past 150 years, with 45 related species. We show that many bread wheat accessions share near-identical haplotype blocks with close relatives of wheat's diploid and tetraploid progenitors, while some show evidence of introgressions from more distant species and structural variation between accessions. Hence, introgressions and chromosomal rearrangements appear to have made a major contribution to genetic diversity in cultivar collections. As gene flow from relatives to bread wheat is an ongoing process, we assess the impact that introgressions might have on future breeding strategies.

RevDate: 2021-02-02

Cho SH, Jeong Y, Lee E, et al (2021)

Assessment of Erythrobacter species diversity through pan-genome analysis with newly isolated Erythrobacter sp. 3-20A1M.

Journal of microbiology and biotechnology pii:jmb.2012.12054 [Epub ahead of print].

Erythrobacter species are extensively studied marine bacteria that produce various carotenoids. Due to their photoheterotrophic ability, it has been suggested that they play a crucial role in marine ecosystems. It is essential to identify the genome sequence and the genes of the species to predict their role in the marine ecosystem. In this study, we report the complete genome sequence of the marine bacterium Erythrobacter sp. 3-20A1M. The genome size was 3.1 Mbp and its GC content was 64.8%. In total, 2998 genetic features were annotated, of which 2882 were annotated as functional coding genes. Using the genetic information of Erythrobacter sp. 3-20A1M, we performed pan-genome analysis with other Erythrobacter species. This revealed highly conserved secondary metabolite biosynthesis-related COG functions across Erythrobacter species. Through subsequent secondary metabolite biosynthetic gene cluster prediction and KEGG analysis, the carotenoid biosynthetic pathway was proven conserved in all Erythrobacter species, except for the spheroidene and spirilloxanthin pathways, which are only found in photosynthetic Erythrobacter species. The presence of virulence genes, especially the plant-algae cell wall degrading genes, revealed that Erythrobacter sp. 3-20A1M is a potential marine plant-algae scavenger.

RevDate: 2021-02-02

Takahashi T, Lee S, S Kim (2021)

Genomic characteristics of Streptococcus agalactiae based on the pan-genome orthologous group analysis according to invasiveness and capsular genotype.

Journal of infection and chemotherapy : official journal of the Japan Society of Chemotherapy pii:S1341-321X(21)00016-7 [Epub ahead of print].

OBJECTIVE: Following the construction of a bacterial pan-genome from the whole genome sequences on a web-based pipeline, all coding DNA sequences (CDSs) can be clustered into pan-genome orthologous groups (POGs), which is a similar approach to comparative genome hybridization on glass microscope slides. We aimed to clarify the genomic characteristics of Streptococcus agalactiae based on the POG analysis.

METHODS: Sixty-six S. agalactiae isolates obtained from invasive specimens (blood and cerebrospinal fluid) and non-invasive specimens (urine and vaginal discharge) between 2010 and 2017 in Korea were subjected to whole genome sequencing (WGS). Based on the WGS data, we conducted the POG analysis and constructed a phylogenetic tree along with capsular polysaccharide (CPS) genotyping. We compared the genomics of invasive vs. non-invasive isolates, as well as CPS III vs. non-CPS III genotypes.

RESULTS: Predicted pan- and core-genome sizes were 3416 and 1658 genes, respectively. We found four clusters consisting of CPS genotypes (III, VIII, Ib/VI, and Ia) in the phylogenetic tree. There were significant differences in two metabolic pathways specific to invasiveness, and in six metabolic pathways specific to CPS III type produced by CDSs.

CONCLUSION: Our observations reveal the pan- and core-genome sizes, four clusters of genomes distributed by CPS genotypes, and unique CDS features of S. agalactiae by comparative genomics in terms of invasiveness and CPS genotype.

RevDate: 2021-02-02

Naorem RS, Blom J, C Fekete (2021)

Genome-wide comparison of four MRSA clinical isolates from Germany and Hungary.

PeerJ, 9:e10185.

Staphylococcus aureus is a drug-resistant pathogen, capable of colonizing diverse ecological niches and causing a broad spectrum of infections related to a community and healthcare. In this study, we choose four methicillin-resistant S. aureus (MRSA) clinical isolates from Germany and Hungary based on our previous polyphasic characterization finding. We assumed that the selected strains have a different genetic background in terms of the presence of resistance and virulence genes, prophages, plasmids, and secondary metabolite biosynthesis genes that may play a crucial role in niche adaptation and pathogenesis. To clarify these assumptions, we performed a comparative genome analysis of these strains and observed many differences in their genomic compositions. The Hungarian isolates (SA H27 and SA H32) with ST22-SCCmec type IVa have fewer genes for multiple-drug resistance, virulence, and prophages reported in Germany isolates. Germany isolate, SA G6 acquires aminoglycoside (ant(6)-Ia and aph(3')-III) and nucleoside (sat-4) resistance genes via phage transduction and may determine its pathogenic potential. The comparative genome study allowed the segregation of isolates of geographical origin and differentiation of the clinical isolates from the commensal isolates. This study suggested that Germany and Hungarian isolates are genetically diverse and showing variation among them due to the gain or loss of mobile genetic elements (MGEs). An interesting finding is the addition of SA G6 genome responsible for the drastic decline of the core/pan-genome ratio curve and causing the pan-genome to open wider. Functional characterizations revealed that S. aureus isolates survival are maintained by the amino acids catabolism and favor adaptation to growing in a protein-rich medium. The dispersible and singleton genes content of S. aureus genomes allows us to understand the genetic variation among the CC5 and CC22 groups. The strains with the same genetic background were clustered together, which suggests that these strains are highly alike; however, comparative genome analysis exposed that the acquisition of phage elements, and plasmids through the events of MGEs transfer contribute to differences in their phenotypic characters. This comparative genome analysis would improve the knowledge about the pathogenic S. aureus strain's characterization, and responsible for clinically important phenotypic differences among the S. aureus strains.

RevDate: 2021-02-02

Li F, Ye Q, Chen M, et al (2020)

Multiplex PCR for the Identification of Pathogenic Listeria in Flammulina velutipes Plant Based on Novel Specific Targets Revealed by Pan-Genome Analysis.

Frontiers in microbiology, 11:634255.

Listeria spp. is an important foodborne disease agent, often found in the fresh mushroom (Flammulina velutipes) and its production environment. The aim of this study was to develop multiplex PCR for rapid identification of Listeria monocytogenes and Listeria ivanovii, and nonpathogenic Listeria in F. velutipes plants. Pan-genome analysis was first used to identify five novel Listeria-specific targets: one for the Listeria genus, one for L. monocytogenes, and three for L. ivanovii. Primers for the novel targets were highly specific in individual reactions. The detection limits were 103-104 CFU/mL, meeting the requirements of molecular detection. A mPCR assay for the identification of pathogenic Listeria, with primers targeting the novel genes specific for Listeria genus (LMOSLCC2755_0944), L. monocytogenes (LMOSLCC2755_0090), and L. ivanovii (queT_1) was then designed. The assay specificity was robustly verified by analyzing nonpathogenic Listeria and non-Listeria spp. strains. The determined detection limits were 2.0 × 103 CFU/mL for L. monocytogenes and 3.4 × 103 CFU/mL for L. ivanovii, for pure culture analysis. Further, the assay detected 7.6 × 104 to 7.6 × 100 CFU/10 g of pathogenic Listeria spiked into F. velutipes samples following 4-12 h enrichment. The assay feasibility was evaluated by comparing with a traditional culture-based method, by analyzing 129 samples collected from different F. velutipes plants. The prevalence of Listeria spp. and L. monocytogenes was 58.1% and 41.1%, respectively. The calculated κ factors for Listeria spp., L. monocytogenes, and L. ivanovii were 0.97, 0.97, and 1, respectively. The results of the novel mPCR assay were highly consistent with those of the culture-based method. The new assay thus will allow rapid, specific, and accurate detection and monitoring of pathogenic Listeria in food and its production environment.

RevDate: 2021-02-11

Molina-Mora JA, Chinchilla-Montero D, García-Batán R, et al (2021)

Genomic context of the two integrons of ST-111 Pseudomonas aeruginosa AG1: A VIM-2-carrying old-acquaintance and a novel IMP-18-carrying integron.

Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases, 89:104740 pii:S1567-1348(21)00037-X [Epub ahead of print].

Pseudomonas aeruginosa is an opportunist and versatile organism responsible for infections mainly in immunocompromised hosts. This pathogen has high intrinsic resistance to most antimicrobials. P. aeruginosa AG1 (PaeAG1) is a Costa Rican high-risk ST-111 strain with resistance to multiple antibiotics, including carbapenems, due to the activity of VIM-2 and IMP-18 metallo-β-lactamases (MBLs). These genes are harbored in two class 1 integrons located inone out of the 57 PaeAG1 genomic islands. However, the genomic context associated to these determinants in PaeAG1 and other P. aeruginosa strains is unclear. Thus, we first assessed the transcriptional activity of VIM-2 and IMP-18 genes when exposed to imipenem (a carbapenem) by RT-qPCR. To select related genomes to PaeAG1, we implemented a pan-genome analysis to define and up-date the phylogenetic relationship among complete P. aeruginosa genomes. We also studied the PaeAG1 genomic islands content in the related strains and finally we described the architecture and possible evolutionary steps of the genomic regions around the VIM-2- and IMP-18-carrying integrons. Expression of VIM-2 and IMP-18 genes was demonstrated to be induced after imipenem exposure. In a subsequent comparative genomics analysis with 211 strains, the P. aeruginosa pan-genome revealed that complete genome sequences are able to separate clones by MLST profile, including a clear ST-111 cluster with PaeAG1. The PaeAG1 genomic islands were found to define a diverse presence/absence pattern among related genomes. Finally, landscape reconstruction of genomic regions showed that VIM-2-carrying integron (In59-like) is an old-acquaintance element harbored in the same known region found in other two ST-111 strains. Also, PaeAG1 has an exclusive genomic region containing a novel IMP-18-carrying integron (registered as In1666), with an arrangement never reported before. Altogether, we provide new insights about the genomic determinants associated with the resistance to carbapenems in this high-risk P. aeruginosa using comparative genomics.

RevDate: 2021-02-06

Vázquez-Rosas-Landa M, Sánchez-Rangel D, Hernández-Domínguez EE, et al (2021)

Design of a diagnostic system based on molecular markers derived from the ascomycetes pan-genome analysis: The case of Fusarium dieback disease.

PloS one, 16(1):e0246079.

A key factor to take actions against phytosanitary problems is the accurate and rapid detection of the causal agent. Here, we develop a molecular diagnostics system based on comparative genomics to easily identify fusariosis and specific pathogenic species as the Fusarium kuroshium, the symbiont of the ambrosia beetle Euwallaceae kuroshio Gomez and Hulcr which is responsible for Fusarium dieback disease in San Diego CA, USA. We performed a pan-genome analysis using sixty-three ascomycetes fungi species including phytopathogens and fungi associated with the ambrosia beetles. Pan-genome analysis revealed that 2,631 orthologue genes are only shared by Fusarium spp., and on average 3,941 (SD ± 1,418.6) are species-specific genes. These genes were used for PCR primer design and tested on DNA isolated from i) different strains of ascomycete species, ii) artificially infected avocado stems and iii) plant tissue of field-collected samples presumably infected. Our results let us propose a useful set of primers to either identify any species from Fusarium genus or, in a specific manner, species such as F. kuroshium, F. oxysporum, and F. graminearum. The results suggest that the molecular strategy employed in this study can be expanded to design primers against different types of pathogens responsible for provoking critical plant diseases.

RevDate: 2021-01-30

Candeliere F, Raimondi S, Spampinato G, et al (2020)

Comparative Genomics of Leuconostoc carnosum.

Frontiers in microbiology, 11:605127.

Leuconostoc carnosum is a known colonizer of meat-related food matrices. It reaches remarkably high loads during the shelf life in packaged meat products and plays a role in spoilage, although preservative effects have been proposed for some strains. In this study, the draft genomes of 17 strains of L. carnosum (i.e., all the strains that have been sequenced so far) were compared to decipher their metabolic and functional potential and to determine their role in food transformations. Genome comparison and pathway reconstruction indicated that L. carnosum is a compact group of closely related heterofermentative bacteria sharing most of the metabolic features. Adaptation to a nitrogen-rich environment, such as meat, is evidenced by 23 peptidase genes identified in the core genome and by the autotrophy for nitrogen compounds including several amino acids, vitamins, and cofactors. Genes encoding the decarboxylases yielding biogenic amines were not present. All the strains harbored 1-4 of 32 different plasmids, bearing functions associated to proteins hydrolysis, transport of amino acids and oligopeptides, exopolysaccharides, and various resistances (e.g., to environmental stresses, bacteriophages, and heavy metals). Functions associated to bacteriocin synthesis, secretion, and immunity were also found in plasmids. While genes for lactococcin were found in most plasmids, only three harbored the genes for leucocin B, a class IIa antilisterial bacteriocin. Determinants of antibiotic resistances were absent in both plasmids and chromosomes.

RevDate: 2021-01-30

Bryan NC, Lebreton F, Gilmore M, et al (2020)

Genomic and Functional Characterization of Enterococcus faecalis Isolates Recovered From the International Space Station and Their Potential for Pathogenicity.

Frontiers in microbiology, 11:515319.

Enterococcus faecalis is a multidrug resistant, opportunistic human pathogen and a leading cause of hospital acquired infections. Recently, isolates have been recovered from the air and surfaces onboard the International Space Station (ISS). Pangenomic and functional analyses were carried out to assess their potential impact on astronaut health. Genomes of each ISS isolate, and both clinical and commensal reference strains, were evaluated for their core and unique gene content, acquired antibiotic resistance genes, phage, plasmid content, and virulence traits. In order to determine their potential survival when outside of the human host, isolates were also challenged with three weeks of desiccation at 30% relative humidity. Finally, pathogenicity of the ISS strains was evaluated in the model organism Caenorhabditis elegans. At the culmination of this study, there were no defining signatures that separated known pathogenic strains from the more commensal phenotypes using the currently available resources. As a result, the current reliance on database information alone must be shifted to experimentally evaluated genotypic and phenotypic characteristics of clinically relevant microorganisms.

RevDate: 2021-02-02

Rajput A, Seif Y, Choudhary KS, et al (2021)

Pangenome Analytics Reveal Two-Component Systems as Conserved Targets in ESKAPEE Pathogens.

mSystems, 6(1):.

The two-component system (TCS) helps bacteria sense and respond to environmental stimuli through histidine kinases and response regulators. TCSs are the largest family of multistep signal transduction processes, and they are involved in many important cellular processes such as antibiotic resistance, pathogenicity, quorum sensing, osmotic stress, and biofilms. Here, we perform the first comprehensive study to highlight the role of TCSs as potential drug targets against ESKAPEE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp., and Escherichia coli) pathogens through annotation, mapping, pangenomic status, gene orientation, and sequence variation analysis. The distribution of the TCSs is group specific with regard to Gram-positive and Gram-negative bacteria, except for KdpDE. The TCSs among ESKAPEE pathogens form closed pangenomes, except for Pseudomonas aeruginosa Furthermore, their conserved nature due to closed pangenomes might make them good drug targets. Fitness score analysis suggests that any mutation in some TCSs such as BaeSR, ArcBA, EvgSA, and AtoSC, etc., might be lethal to the cell. Taken together, the results of this pangenomic assessment of TCSs reveal a range of strategies deployed by the ESKAPEE pathogens to manifest pathogenicity and antibiotic resistance. This study further suggests that the conserved features of TCSs might make them an attractive group of potential targets with which to address antibiotic resistance.IMPORTANCE The ESKAPEE pathogens are the leading cause of health care-associated infections worldwide. Two-component systems (TCSs) can be used as effective targets against pathogenic bacteria since they are ubiquitous and manage various vital functions such as antibiotic resistance, virulence, biofilms, quorum sensing, and pH balance, among others. This study provides a comprehensive overview of the pangenomic status of the TCSs among ESKAPEE pathogens. The annotation and pangenomic analysis of TCSs show that they are significantly distributed and conserved among the pathogens, as most of them form closed pangenomes. Furthermore, our analysis also reveals that the removal of the TCSs significantly affects the fitness of the cell. Hence, they may be used as promising drug targets against bacteria.

RevDate: 2021-01-26

Freitas-Silva J, de Oliveira BFR, Vigoder FM, et al (2020)

Peeling the Layers Away: The Genomic Characterization of Bacillus pumilus 64-1, an Isolate With Antimicrobial Activity From the Marine Sponge Plakina cyanorosea (Porifera, Homoscleromorpha).

Frontiers in microbiology, 11:592735.

Bacillus pumilus 64-1, a bacterial strain isolated from the marine sponge Plakina cyanorosea, which exhibits antimicrobial activity against both pathogenic and drug-resistant Gram-positive and Gram-negative bacteria. This study aimed to conduct an in-depth genomic analysis of this bioactive sponge-derived strain. The nearly complete genome of strain 64-1 consists of 3.6 Mbp (41.5% GC), which includes 3,705 coding sequences (CDS). An open pangenome was observed when limiting to the type strains of the B. pumilus group and aquatic-derived B. pumilus representatives. The genome appears to encode for at least 12 potential biosynthetic gene clusters (BGCs), including both types I and III polyketide synthases (PKS), non-ribosomal peptide synthetases (NRPS), and one NRPS-T1PKS hybrid, among others. In particular, bacilysin and other bacteriocin-coding genes were found and may be associated with the detected antimicrobial activity. Strain 64-1 also appears to possess a broad repertoire of genes encoding for plant cell wall-degrading carbohydrate-active enzymes (CAZymes). A myriad of genes which may be involved in various process required by the strain in its marine habitat, such as those encoding for osmoprotectory transport systems and the biosynthesis of compatible solutes were also present. Several heavy metal tolerance genes are also present, together with various mobile elements including a region encoding for a type III-B Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) region, four prophage segments and transposase elements. This is the first report on the genomic characterization of a cultivable bacterial member of the Plakina cyanorosea holobiont.

RevDate: 2021-02-13

Jayakodi M, Schreiber M, Stein N, et al (2021)

Building pan-genome infrastructures for crop plants and their use in association genetics.

DNA research : an international journal for rapid publication of reports on genes and genomes, 28(1):.

Pan-genomic studies aim at representing the entire sequence diversity within a species to provide useful resources for evolutionary studies, functional genomics and breeding of cultivated plants. Cost reductions in high-throughput sequencing and advances in sequence assembly algorithms have made it possible to create multiple reference genomes along with a catalogue of all forms of genetic variations in plant species with large and complex or polyploid genomes. In this review, we summarize the current approaches to building pan-genomes as an in silico representation of plant sequence diversity and outline relevant methods for their effective utilization in linking structural with phenotypic variation. We propose as future research avenues (i) transcriptomic and epigenomic studies across multiple reference genomes and (ii) the development of user-friendly and feature-rich pan-genome browsers.

RevDate: 2021-01-27

Ruiz-Roldán L, de Toro M, Y Sáenz (2021)

Whole Genome Analysis of Environmental Pseudomonas mendocina Strains: Virulence Mechanisms and Phylogeny.

Genes, 12(1):.

Pseudomonas mendocina is an environmental bacterium, rarely isolated in clinical specimens, although it has been described as producing endocarditis and sepsis. Little is known about its genome. Whole genome sequencing can be used to learn about the phylogeny, evolution, or pathogenicity of these isolates. Thus, the aim of this study was to analyze the resistome, virulome, and phylogenetic relationship of two P. mendocina strains, Ps542 and Ps799, isolated from a healthy Anas platyrhynchos fecal sample and a lettuce, respectively. Among all of the small number of P.mendocina genomes available in the National Center for Biotechnology Information (NCBI) repository, both strains were placed within one of two well-defined phylogenetic clusters. Both P. mendocina strains lacked antimicrobial resistance genes, but the Ps799 genome showed a MOBP3 family relaxase. Nevertheless, this study revealed that P. mendocina possesses an important number of virulence factors, including a leukotoxin, flagella, pili, and the Type 2 and Type 6 Secretion Systems, that could be responsible for their pathogenesis. More phenotypical and in vivo studies are needed to deepen the association with human infections and the potential P. mendocina pathogenicity.

RevDate: 2021-01-26

Guardiola-Avila I, Sánchez-Busó L, Acedo-Félix E, et al (2021)

Core and Accessory Genome Analysis of Vibrio mimicus.

Microorganisms, 9(1):.

Vibrio mimicus is an emerging pathogen, mainly associated with contaminated seafood consumption. However, little is known about its evolution, biodiversity, and pathogenic potential. This study analyzes the pan-, core, and accessory genomes of nine V. mimicus strains. The core genome yielded 2424 genes in chromosome I (ChI) and 822 genes in chromosome II (ChII), with an accessory genome comprising an average of 10.9% of the whole genome for ChI and 29% for ChII. Core genome phylogenetic trees were obtained, and V. mimicus ATCC-33654 strain was the closest to the outgroup in both chromosomes. Additionally, a phylogenetic study of eight conserved genes (ftsZ, gapA, gyrB, topA, rpoA, recA, mreB, and pyrH), including Vibrio cholerae, Vibrio parilis, Vibrio metoecus, and Vibrio caribbenthicus, clearly showed clade differentiation. The main virulence genes found in ChI corresponded with type I secretion proteins, extracellular components, flagellar proteins, and potential regulators, while, in ChII, the main categories were type-I secretion proteins, chemotaxis proteins, and antibiotic resistance proteins. The accessory genome was characterized by the presence of mobile elements and toxin encoding genes in both chromosomes. Based on the genome atlas, it was possible to characterize differential regions between strains. The pan-genome of V. mimicus encompassed 3539 genes for ChI and 2355 genes for ChII. These results give us an insight into the virulence and gene content of V. mimicus, as well as constitute the first approach to its diversity.

RevDate: 2021-01-18

Pais AKL, Silva JRD, Santos LVSD, et al (2021)

Genomic sequencing of different sequevars of Ralstonia solanacearum belonging to the Moko ecotype.

Genetics and molecular biology, 44(1):e20200172 pii:S1415-47572021000100402.

Banana vascular wilt or Moko is a disease caused by Ralstonia solanacearum. This study aimed to sequence, assemble, annotate, and compare the genomes of R. solanacearum Moko ecotypes of different sequevar strains from Brazil. Average nucleotide identity analyses demonstrated a high correlation (> 96%) between the genome sequences of strains CCRMRs277 (sequevar IIA-24), CCRMRs287 (IIB-4), CCRMRs304 (IIA-24), and CCRMRsB7 (IIB-25), which were grouped into phylotypes IIA and IIB. The number of coding sequences present in chromosomes and megaplasmids varied from 3,070 to 3,521 and 1,669 to 1,750, respectively. Pangenome analysis identified 3,378 clusters in the chromosomes, of which 2,604 were shared by all four analyzed genomes and 2,580 were single copies. In megaplasmids, 1,834 clusters were identified, of which 1,005 were shared by all four genomes and 992 were identified as single copies. Strains CCRMRsB7 and CCRMRs287 differed from the others by having unique clusters in both their chromosomes and megaplasmids, and CCRMRsB7 possessed the largest genome among all Moko ecotype strains sequenced to date. Therefore, the genomic information obtained in this study provides a theoretical basis for the identification, characterization, and phylogenetic analysis of R. solanacearum Moko ecotypes.

RevDate: 2021-01-29
CmpDate: 2021-01-29

Rai A, Hirakawa H, Nakabayashi R, et al (2021)

Chromosome-level genome assembly of Ophiorrhiza pumila reveals the evolution of camptothecin biosynthesis.

Nature communications, 12(1):405.

Plant genomes remain highly fragmented and are often characterized by hundreds to thousands of assembly gaps. Here, we report chromosome-level reference and phased genome assembly of Ophiorrhiza pumila, a camptothecin-producing medicinal plant, through an ordered multi-scaffolding and experimental validation approach. With 21 assembly gaps and a contig N50 of 18.49 Mb, Ophiorrhiza genome is one of the most complete plant genomes assembled to date. We also report 273 nitrogen-containing metabolites, including diverse monoterpene indole alkaloids (MIAs). A comparative genomics approach identifies strictosidine biogenesis as the origin of MIA evolution. The emergence of strictosidine biosynthesis-catalyzing enzymes precede downstream enzymes' evolution post γ whole-genome triplication, which occurred approximately 110 Mya in O. pumila, and before the whole-genome duplication in Camptotheca acuminata identified here. Combining comparative genome analysis, multi-omics analysis, and metabolic gene-cluster analysis, we propose a working model for MIA evolution, and a pangenome for MIA biosynthesis, which will help in establishing a sustainable supply of camptothecin.

RevDate: 2021-01-17

Bravakos P, Mandalakis M, Nomikou P, et al (2021)

Genomic adaptation of Pseudomonas strains to acidity and antibiotics in hydrothermal vents at Kolumbo submarine volcano, Greece.

Scientific reports, 11(1):1336.

Although the rise of antibiotic and multidrug resistant bacteria is one of the biggest current threats to human health, our understanding of the mechanisms involved in antibiotic resistance selection remains scarce. We performed whole genome sequencing of 21 Pseudomonas strains, previously isolated from an active submarine volcano of Greece, the Kolumbo volcano. Our goal was to identify the genetic basis of the enhanced co-tolerance to antibiotics and acidity of these Pseudomonas strains. Pangenome analysis identified 10,908 Gene Clusters (GCs). It revealed that the numbers of phage-related GCs and sigma factors, which both provide the mechanisms of adaptation to environmental stressors, were much higher in the high tolerant Pseudomonas strains compared to the rest ones. All identified GCs of these strains were associated with antimicrobial and multidrug resistance. The present study provides strong evidence that the CO2-rich seawater of the volcano associated with low pH might be a reservoir of microorganisms carrying multidrug efflux-mediated systems and pumps. We, therefore, suggest further studies of other extreme environments (or ecosystems) and their associated physicochemical parameters (or factors) in the rise of antibiotic resistance.

RevDate: 2021-01-13

Heaton MP, Smith TPL, Bickhart DM, et al (2021)

A reference genome assembly of Simmental cattle, Bos taurus taurus.

The Journal of heredity pii:6092654 [Epub ahead of print].

Genomics research has relied principally on the establishment and curation of a reference genome for the species. However, it is increasingly recognized that a single reference genome cannot fully describe the extent of genetic variation within many widely-distributed species. Pangenome representations are based on high-quality genome assemblies of multiple individuals and intended to represent the broadest possible diversity within a species. A Bovine Pangenome Consortium (BPC) has recently been established to begin assembling genomes from more than 600 recognized breeds of cattle, together with other related species to provide information on ancestral alleles and haplotypes. Previously reported de novo genome assemblies for Angus, Brahman, Hereford, and Highland breeds of cattle are part of the initial BPC effort. The present report describes a complete single haplotype assembly at chromosome-scale for a fullblood Simmental cow from an F1 bison-cattle hybrid fetus by trio binning. Simmental cattle, also known as Fleckvieh due to their red and white spots, originated in central Europe in the 1830's as a triple-purpose breed selected for draught, meat, and dairy production. There are over 50 million Simmental cattle in the world, known today for their fast growth and beef yields. This assembly (ARS_Simm1.0) is similar in length to the other bovine assemblies at 2.86 Gb, with a scaffold N50 of 102 Mb (max scaffold 156.8 Mb) and meets or exceeds the continuity of the best B. taurus reference assemblies to date.

RevDate: 2021-01-12

Hasan NA, Norton GJ, Virdi R, et al (2021)

Measurable genomic changes in Mycobacterium avium subsp. hominissuis after long-term adaptation in Acanthamoeba lenticulata and reduced persistence in macrophages.

Journal of bacteriology pii:JB.00257-20 [Epub ahead of print].

Free-living amoebae are ubiquitous in aquatic environments and act as environmental reservoirs for nontuberculous mycobacteria. Mycobacterium avium subsp. hominissuis recovered from Acanthamoeba has been demonstrated to be more virulent in both human and murine models. Here, we investigate the persistence of M. avium subsp. hominissuis after short-term (2 weeks) and long-term (42 weeks) co-culture in Acanthamoeba lenticulata We hypothesize that A. lenticulata-adapted M. avium subsp. hominissuis demonstrate phenotypic and genomic changes facilitating intracellular persistence in naïve Acanthamoeba and human macrophages. M. avium subsp. hominissuis CFU in co-culture with A. lenticulata were recorded every 2 weeks up to 60 weeks. While A. lenticulata-associated M. avium subsp. hominissuis CFU did not significantly change across 60 weeks of co-culture, longer adaptation time in amoebae reduced colony size. Isolates recovered after 2 or 42 weeks of amoebae co-culture were referred as "early-adapted" and "late-adapted" M. avium subsp. hominissuis, respectively. Whole genome sequencing was performed on amoebae-adapted isolates with pan-genome comparisons to the original M. avium subsp. hominissuis isolate. Next, amoebae-adapted isolates were assessed for their persistence in A. lenticulata,A. castellanii, and human THP-1 macrophages. Multiplex cytokine/chemokine analyses were conducted on THP-1 culture supernatants. Compared to the original isolate, counts of late-adapted M. avium subsp. hominissuis were reduced in Acanthamoeba and contrary to expectations, lower counts were also observed in THP-1 macrophages with concomitant decrease in TNFa, IL-6, and MIP-1b suggesting that host adaptation may influence the inflammatory properties of M. aviumIMPORTANCE Short-term interaction between Acanthamoeba and M. avium has been demonstrated to increase infectivity in human and murine models of infection, establishing the paradigm that amoebae "train" M. avium in the environment by selecting for phenotypes capable of enduring in human cells. We investigate this phenomenon further by determining the consequence of long-term amoebae adaptation on M. avium subsp. hominissuis persistence in host cells. We monitored genomic changes across long-term Acanthamoeba co-culture and report significant changes to the M. avium subsp. hominissuis genome in response to amoebae-adaptation and reduced colony size. Furthermore, we examined isolates co-cultured with A. lenticulata for 2 or 42 weeks and provide biological evidence that long-term co-culture in amoebae reduces M. avium persistence in human macrophages.

RevDate: 2021-01-26

Firrao G, Scortichini M, L Pagliari (2021)

Orthology-Based Estimate of the Contribution of Horizontal Gene Transfer from Distantly Related Bacteria to the Intraspecific Diversity and Differentiation of Xylella fastidiosa.

Pathogens (Basel, Switzerland), 10(1):.

Xylella fastidiosa is a xylem-limited bacterium phylogenetically related to the xanthomonads, with an unusually large and diversified range of plant hosts. To ascertain the origin of its peculiarities, its pan-genome was scanned to identify the genes that are not coherent with its phylogenetic position within the order Xanthomonadales. The results of the analysis revealed that a large fraction of the genes of the Xylella pan-genome have no ortholog or close paralog in the order Xanthomonadales. For a significant part of the genes, the closest homologue was found in bacteria belonging to distantly related taxonomic groups, most frequently in the Betaproteobacteria. Other species, such as Xanthomonas vasicola and Xanthomonas albilineans which were investigated for comparison, did not show a similar genetic contribution from distant branches of the prokaryotic tree of life. This finding indicates that the process of acquisition of DNA from the environment is still a relevant component of Xylella fastidiosa evolution. Although the ability of Xylella fastidiosa strains to recombine among themselves is well known, the results of the pan-genome analyses stressed the additional relevance of environmental DNA in shaping their genomes, with potential consequences on their phytopathological features.

RevDate: 2021-01-11

Du H, Diao C, Zhao P, et al (2021)

Integrated hybrid de novo assembly technologies to obtain high-quality pig genome using short and long reads.

Briefings in bioinformatics pii:6082823 [Epub ahead of print].

With the rapid progress of sequencing technologies, various types of sequencing reads and assembly algorithms have been designed to construct genome assemblies. Although recent studies have attempted to evaluate the appropriate type of sequencing reads and algorithms for assembling high-quality genomes, it is still a challenge to set the correct combination for constructing animal genomes. Here, we present a comparative performance assessment of 14 assembly combinations-9 software programs with different short and long reads of Duroc pig. Based on the results of the optimization process for genome construction, we designed an integrated hybrid de novo assembly pipeline, HSCG, and constructed a draft genome for Duroc pig. Comparison between the new genome and Sus scrofa 11.1 revealed important breakpoints in two S. scrofa 11.1 genes. Our findings may provide new insights into the pan-genome analysis studies of agricultural animals, and the integrated assembly pipeline may serve as a guide for the assembly of other animal genomes.

RevDate: 2021-01-11

Harrison F, AR Smyth (2021)

Professor Pangloss and the Pangenome: Does Staphylococcus aureus Have the Best of All Possible Worlds?.

American journal of respiratory and critical care medicine [Epub ahead of print].

RevDate: 2021-02-13

Wang M, Ruan R, H Li (2021)

The completed genome sequence of the pathogenic ascomycete fungus Penicillium digitatum.

Genomics, 113(2):439-446 pii:S0888-7543(21)00001-X [Epub ahead of print].

P. digitatum, the causative agent of green mold, is one of the most destructive pathogens in the citrus industry. To facilitate basal researches on this important plant pathogen, here we report a finished genome sequence for P. digitatum strain PDW03 using a combination of Illumina, PacBio, and Hi-C sequencing technologies. The assembly comprised 6 chromosomes from telomere to telomere and encodes approximately 9000 proteins. Genomic re-analyses identified 302 Carbohydrate-active enzymes, 420 secreted proteins, and 39 secondary metabolite (SM) gene clusters. Furthermore, we found 10 fragmentary SM clusters in the P. digitatum PDW03 genome. Pangenome analysis based on 5 P. digitatum genomes available showed that conserved orthogroups account for ~68% of the species pangenome. Taken together, this fully completed P. digitatum genome will provide an optimum resource for further researches to investigate the driving forces of fungal host switch and effectors functioning in plant-pathogen interaction.

RevDate: 2021-01-11

Higdon SM, Huang BC, Bennett AB, et al (2020)

Identification of Nitrogen Fixation Genes in Lactococcus Isolated from Maize Using Population Genomics and Machine Learning.

Microorganisms, 8(12):.

Sierra Mixe maize is a landrace variety from Oaxaca, Mexico, that utilizes nitrogen derived from the atmosphere via an undefined nitrogen fixation mechanism. The diazotrophic microbiota associated with the plant's mucilaginous aerial root exudate composed of complex carbohydrates was previously identified and characterized by our group where we found 23 lactococci capable of biological nitrogen fixation (BNF) without containing any of the proposed essential genes for this trait (nifHDKENB). To determine the genes in Lactococcus associated with this phenotype, we selected 70 lactococci from the dairy industry that are not known to be diazotrophic to conduct a comparative population genomic analysis. This showed that the diazotrophic lactococcal genomes were distinctly different from the dairy isolates. Examining the pangenome followed by genome-wide association study and machine learning identified genes with the functions needed for BNF in the maize isolates that were absent from the dairy isolates. Many of the putative genes received an 'unknown' annotation, which led to the domain analysis of the 135 homologs. This revealed genes with molecular functions needed for BNF, including mucilage carbohydrate catabolism, glycan-mediated host adhesion, iron/siderophore utilization, and oxidation/reduction control. This is the first report of this pathway in this organism to underpin BNF. Consequently, we proposed a model needed for BNF in lactococci that plausibly accounts for BNF in the absence of the nif operon in this organism.

RevDate: 2021-01-08

Horesh G, Blackwell GA, Tonkin-Hill G, et al (2021)

A comprehensive and high-quality collection of Escherichia coli genomes and their genes.

Microbial genomics [Epub ahead of print].

RevDate: 2021-01-12

Nzoyikorera N, Diawara I, Fresia P, et al (2021)

Whole genomic comparative analysis of Streptococcus pneumoniae serotype 1 isolates causing invasive and non-invasive infections among children under 5 years in Casablanca, Morocco.

BMC genomics, 22(1):39.

BACKGROUND: Streptococcus pneumoniae serotype 1 remains a leading cause of invasive pneumococcal diseases, even in countries with PCV-10/PCV-13 vaccine implementation. The main objective of this study, which is part of the Pneumococcal African Genome project (PAGe), was to determine the phylogenetic relationships of serotype 1 isolates recovered from children patients in Casablanca (Morocco), compared to these from other African countries; and to investigate the contribution of accessory genes and recombination events to the genetic diversity of this serotype.

RESULTS: The genome average size of the six-pneumococcus serotype 1 from Casablanca was 2,227,119 bp, and the average content of coding sequences was 2113, ranging from 2041 to 2161. Pangenome analysis of the 80 genomes used in this study revealed 1685 core genes and 1805 accessory genes. The phylogenetic tree based on core genes and the hierarchical bayesian clustering analysis revealed five sublineages with a phylogeographic structure by country. The Moroccan strains cluster in two different lineages, the five invasive strains clusters altogether in a divergent clade distantly related to the non-invasive strain, that cluster with all the serotype 1 genomes from Africa.

CONCLUSIONS: The whole genome sequencing provides increased resolution analysis of the highly virulent serotype 1 in Casablanca, Morocco. Our results are concordant with previous works, showing that the phylogeography of S. pneumoniae serotype 1 is structured by country, and despite the small size (six isolates) of the Moroccan sample, our analysis shows the genetic cohesion of the Moroccan invasive isolates.

RevDate: 2021-01-15
CmpDate: 2021-01-13

Yahara K, Suzuki M, Hirabayashi A, et al (2021)

Long-read metagenomics using PromethION uncovers oral bacteriophages and their interaction with host bacteria.

Nature communications, 12(1):27.

Bacteriophages (phages), or bacterial viruses, are very diverse and highly abundant worldwide, including as a part of the human microbiomes. Although a few metagenomic studies have focused on oral phages, they relied on short-read sequencing. Here, we conduct a long-read metagenomic study of human saliva using PromethION. Our analyses, which integrate both PromethION and HiSeq data of >30 Gb per sample with low human DNA contamination, identify hundreds of viral contigs; 0-43.8% and 12.5-56.3% of the confidently predicted phages and prophages, respectively, do not cluster with those reported previously. Our analyses demonstrate enhanced scaffolding, and the ability to place a prophage in its host genomic context and enable its taxonomic classification. Our analyses also identify a Streptococcus phage/prophage group and nine jumbo phages/prophages. 86% of the phage/prophage group and 67% of the jumbo phages/prophages contain remote homologs of antimicrobial resistance genes. Pan-genome analysis of the phages/prophages reveals remarkable diversity, identifying 0.3% and 86.4% of the genes as core and singletons, respectively. Furthermore, our study suggests that oral phages present in human saliva are under selective pressure to escape CRISPR immunity. Our study demonstrates the power of long-read metagenomics utilizing PromethION in uncovering bacteriophages and their interaction with host bacteria.

RevDate: 2021-01-11

Della Coletta R, Qiu Y, Ou S, et al (2021)

How the pan-genome is changing crop genomics and improvement.

Genome biology, 22(1):3.

Crop genomics has seen dramatic advances in recent years due to improvements in sequencing technology, assembly methods, and computational resources. These advances have led to the development of new tools to facilitate crop improvement. The study of structural variation within species and the characterization of the pan-genome has revealed extensive genome content variation among individuals within a species that is paradigm shifting to crop genomics and improvement. Here, we review advances in crop genomics and how utilization of these tools is shifting in light of pan-genomes that are becoming available for many crop species.

RevDate: 2021-01-26

Fontana F, Alessandri G, Lugli GA, et al (2020)

Probiogenomics Analysis of 97 Lactobacilluscrispatus Strains as a Tool for the Identification of Promising Next-Generation Probiotics.

Microorganisms, 9(1):.

Members of the genus Lactobacillus represent the most common colonizers of the human vagina and are well-known for preserving vaginal health and contrasting the colonization of opportunistic pathogens. Remarkably, high abundance of Lactobacillus crispatus in the vaginal environment has been linked to vaginal health, leading to the widespread use of many L. crispatus strains as probiotics. Nevertheless, despite the scientific and industrial relevance of this species, a comprehensive investigation of the genomics of L. crispatus taxon is still missing. For this reason, we have performed a comparative genomics analysis of 97 L. crispatus strains, encompassing 16 strains sequenced in the framework of this study alongside 81 additional publicly available genome sequences. Thus, allowing the dissection of the L.crispatus pan-genome and core-genome followed by a comprehensive phylogenetic analysis based on the predicted core genes that revealed clustering based on ecological origin. Subsequently, a genomics-targeted approach, i.e., probiogenomics analysis, was applied for in-depth analysis of the eight L. crispatus strains of human origin sequenced in this study. In detail their genetic repertoire was screened for strain-specific genes responsible for phenotypic features that may guide the identification of optimal candidates for next-generation probiotics. The latter includes bacteriocin production, carbohydrates transport and metabolism, as well as a range of features that may be responsible for improved ecological fitness. In silico results regarding the genetic repertoire involved in carbohydrate metabolism were also validated by growth assays on a range of sugars, leading to the selection of putative novel probiotic strains.

RevDate: 2021-01-26

Wibberg D, Price-Carter M, Rückert C, et al (2020)

Complete Genome Sequence of Ovine Mycobacterium avium subsp. paratuberculosis Strain JIII-386 (MAP-S/type III) and Its Comparison to MAP-S/type I, MAP-C, and M. avium Complex Genomes.

Microorganisms, 9(1):.

Mycobacterium avium (M. a.) subsp. paratuberculosis (MAP) is a worldwide-distributed obligate pathogen in ruminants causing Johne's disease. Due to a lack of complete subtype III genome sequences, there is not yet conclusive information about genetic differences between strains of cattle (MAP-C, type II) and sheep (MAP-S) type, and especially between MAP-S subtypes I, and III. Here we present the complete, circular genome of MAP-S/type III strain JIII-386 (DE) closed by Nanopore-technology and its comparison with MAP-S/type I closed genome of strain Telford (AUS), MAP-S/type III draft genome of strain S397 (U.S.), twelve closed MAP-C strains, and eight closed M.-a.-complex-strains. Structural comparative alignments revealed clearly the mosaic nature of MAP, emphasized differences between the subtypes and the higher diversity of MAP-S genomes. The comparison of various genomic elements including transposases and genomic islands provide new insights in MAP genomics. MAP type specific phenotypic features may be attributed to genes of known large sequence polymorphisms (LSPS s) regions I-IV and deletions #1 and #2, confirmed here, but could also result from identified frameshifts or interruptions of various virulence-associated genes (e.g., mbtC in MAP-S). Comprehensive core and pan genome analysis uncovered unique genes (e.g., cytochromes) and genes probably acquired by horizontal gene transfer in different MAP-types and subtypes, but also emphasized the highly conserved and close relationship, and the complex evolution of M.-a.-strains.

RevDate: 2021-01-26

Yang SM, Baek J, Kim E, et al (2020)

Development of a Genoserotyping Method for Salmonella Infantis Detection on the Basis of Pangenome Analysis.

Microorganisms, 9(1):.

In recent years, Salmonella Infantis has become a predominant serovariant in clinical and poultry isolates, thereby imposing a substantial economic burden on both public health and the livestock industry. With the aim of coping with the steep increase in serovar Infantis prevalence, a polymerase chain reaction (PCR)-based rapid and accurate diagnostic assay was developed in this study through pangenome profiling of 60 Salmonella serovars. A gene marker, SIN_02055, was identified, which is present in the S. Infantis genome but not in the pangenome of the other serovars. Primers specific to SIN_02055 were used to accurately detect serovar Infantis, and to successfully differentiate Infantis from the other 59 serovars in real-time PCR with a R2 of 0.999 and an efficiency of 95.76%. The developed method was applied to 54 Salmonella strains belonging to eight dominant serovars, and distinguished Infantis from the other seven serovars with an accuracy of 100%. The diagnostic primer set also did not show false positive amplification with 32 strains from eight non-Salmonella bacterial species. This cost-effective and rapid method can be considered an alternative to the classic serotyping using antisera.

RevDate: 2020-12-31

Bazin A, Gautreau G, Médigue C, et al (2020)

panRGP: a pangenome-based method to predict genomic islands and explore their diversity.

Bioinformatics (Oxford, England), 36(Supplement_2):i651-i658.

MOTIVATION: Horizontal gene transfer (HGT) is a major source of variability in prokaryotic genomes. Regions of genome plasticity (RGPs) are clusters of genes located in highly variable genomic regions. Most of them arise from HGT and correspond to genomic islands (GIs). The study of those regions at the species level has become increasingly difficult with the data deluge of genomes. To date, no methods are available to identify GIs using hundreds of genomes to explore their diversity.

RESULTS: We present here the panRGP method that predicts RGPs using pangenome graphs made of all available genomes for a given species. It allows the study of thousands of genomes in order to access the diversity of RGPs and to predict spots of insertions. It gave the best predictions when benchmarked along other GI detection tools against a reference dataset. In addition, we illustrated its use on metagenome assembled genomes by redefining the borders of the leuX tRNA hotspot, a well-studied spot of insertion in Escherichia coli. panRPG is a scalable and reliable tool to predict GIs and spots making it an ideal approach for large comparative studies.

The methods presented in the current work are available through the following software: https://github.com/labgem/PPanGGOLiN. Detailed results and scripts to compute the benchmark metrics are available at https://github.com/axbazin/panrgp_supdata.

RevDate: 2021-01-26

Surachat K, Kantachote D, Deachamag P, et al (2020)

Genomic Insight into Pediococcus acidilactici HN9, a Potential Probiotic Strain Isolated from the Traditional Thai-Style Fermented Beef Nhang.

Microorganisms, 9(1):.

Pediococcus acidilactici HN9 is a beneficial lactic acid bacterium isolated from Nhang, a traditional Thai-style fermented beef. In this study, the molecular properties of P. acidilactici HN9 were characterized to provide insights into its potential probiotic activity. Specifically, this work sought to report the complete genome of P. acidilactici HN9 and perform a comparative genome analysis with other bacterial strains belonging to the genus Pediococcus. Genomic features of HN9 were compared with those of all other bacterial Pediococcus strains to examine the adaptation, evolutionary relationships, and diversity within this genus. Additionally, several bioinformatic approaches were used to investigate phylogenetic relationships, genome stability, virulence factors, bacteriocin production, and antimicrobial resistance genes of the HN9 strain, as well as to ensure its safety as a potential starter culture in food applications. A 2,034,522 bp circular chromosome and two circular plasmids, designated pHN9-1 (42,239-bp) and pHN9-2 (30,711-bp), were detected, and used for pan-genome analysis, as well as for identification of bacteriocin-encoding genes in 129 strains belonging to all Pediococcus species. Two CRISPR regions were identified in P. acidilactici HN9, including type II-A CRISPR/CRISPR-associated (Cas). This study provides an in-depth analysis on P. acidilactici HN9, facilitating a better understanding of its adaptability to different environments and its mechanism to maintain genome stability over time.

RevDate: 2021-01-01

Blesa A, Baquedano I, González-de la Fuente S, et al (2020)

Integrative and Conjugative Element ICETh1 Functions as a Pangenomic DNA Capture Module in Thermus thermophilus.

Microorganisms, 8(12):.

Transjugation is an unconventional conjugation mechanism in Thermus thermophilus (Tth) that involves the active participation of both mating partners, encompassing a DNA secretion system (DSS) in the donor and an active natural competence apparatus (NCA) in the recipient cells. DSS is encoded within an integrative and conjugative element (ICETh1) in the strain Tth HB27, whereas the NCA is constitutively expressed in both mates. Previous experiments suggested the presence of multiple origins of transfer along the genome, which could generate genomic mosaicity among the progeny. Here, we designed transjugation experiments between two closely related strains of Tth with highly syntenic genomes, containing enough single nucleotide polymorphisms to allow precise parenthood analysis. Individual clones from the progeny were sequenced, revealing their origin as derivatives of our ICETh1-containing intended "donor" strain (HB27), which had acquired separate fragments from the genome of the ICETh1-free HB8 cells, which are our intended recipient. Due to the bidirectional nature of transjugation, only assays employing competence-defective HB27 derivatives as donors allowed the recovery of HB8-derived progeny. These results show a preference for a retrotransfer mechanism in transjugation in ICETh1-bearing strains, supporting an inter-strain gene-capture function for ICETh1. This function could benefit the donor-capable host by facilitating the acquisition of adaptive traits from external sources, ultimately increasing the open pangenome of Thermus, maximizing the potential repertoire of physiological and phenotypical traits related to adaptation and speciation.

RevDate: 2020-12-29

Verma DK, Chaudhary C, Singh L, et al (2020)

Isolation and Taxonomic Characterization of Novel Haloarchaeal Isolates From Indian Solar Saltern: A Brief Review on Distribution of Bacteriorhodopsins and V-Type ATPases in Haloarchaea.

Frontiers in microbiology, 11:554927.

Haloarchaea inhabit high salinity environments worldwide. They are a potentially rich source of crucial biomolecules like carotenoids and industrially useful proteins. However, diversity in haloarchaea present in Indian high salinity environments is poorly studied. In the present study, we isolated 12 haloarchaeal strains from hypersaline Kottakuppam, Tamil Nadu solar saltern in India. 16S rRNA based taxonomic characterization of these isolates suggested that nine of them are novel strains that belong to genera Haloarcula, Halomicrobium, and Haloferax. Transmission electron microscopy suggests the polymorphic nature of these haloarchaeal isolates. Most of the haloarchaeal species are known to be high producers of carotenoids. We were able to isolate carotenoids from all these 12 isolates. The UV-Vis spectroscopy-based analysis suggests that bacterioruberin and lycopene are the major carotenoids produced by these isolates. Based on the visual inspection of the purified carotenoids, the isolates were classified into two broad categories i.e., yellow and orange, attributed to the differences in the ratio of bacterioruberin and lycopene as confirmed by the UV-Vis spectral analysis. Using a PCR-based screening assay, we were able to detect the presence of the bacteriorhodopsin gene (bop) in 11 isolates. We performed whole-genome sequencing for three bop positive and one bop negative haloarchaeal isolates. Whole-genome sequencing, followed by pan-genome analysis identified multiple unique genes involved in various biological functions. We also successfully cloned, expressed, and purified functional recombinant bacteriorhodopsin (BR) from one of the isolates using Escherichia coli as an expression host. BR has light-driven proton pumping activity resulting in the proton gradient across the membrane, which is utilized by V-Type ATPases to produce ATP. We analyzed the distribution of bop and other accessory genes involved in functional BR expression and ATP synthesis in all the representative haloarchaeal species. Our bioinformatics-based analysis of all the sequenced members of genus Haloarcula suggests that bop, if present, is usually inserted between the genes coding for B and D subunits of the V-type ATPases operon. This study provides new insights into the genomic variations in haloarchaea and reports expression of new BR variant having good expression in functional form in E. coli.


RJR Experience and Expertise


Robbins holds BS, MS, and PhD degrees in the life sciences. He served as a tenured faculty member in the Zoology and Biological Science departments at Michigan State University. He is currently exploring the intersection between genomics, microbial ecology, and biodiversity — an area that promises to transform our understanding of the biosphere.


Robbins has extensive experience in college-level education: At MSU he taught introductory biology, genetics, and population genetics. At JHU, he was an instructor for a special course on biological database design. At FHCRC, he team-taught a graduate-level course on the history of genetics. At Bellevue College he taught medical informatics.


Robbins has been involved in science administration at both the federal and the institutional levels. At NSF he was a program officer for database activities in the life sciences, at DOE he was a program officer for information infrastructure in the human genome project. At the Fred Hutchinson Cancer Research Center, he served as a vice president for fifteen years.


Robbins has been involved with information technology since writing his first Fortran program as a college student. At NSF he was the first program officer for database activities in the life sciences. At JHU he held an appointment in the CS department and served as director of the informatics core for the Genome Data Base. At the FHCRC he was VP for Information Technology.


While still at Michigan State, Robbins started his first publishing venture, founding a small company that addressed the short-run publishing needs of instructors in very large undergraduate classes. For more than 20 years, Robbins has been operating The Electronic Scholarly Publishing Project, a web site dedicated to the digital publishing of critical works in science, especially classical genetics.


Robbins is well-known for his speaking abilities and is often called upon to provide keynote or plenary addresses at international meetings. For example, in July, 2012, he gave a well-received keynote address at the Global Biodiversity Informatics Congress, sponsored by GBIF and held in Copenhagen. The slides from that talk can be seen HERE.


Robbins is a skilled meeting facilitator. He prefers a participatory approach, with part of the meeting involving dynamic breakout groups, created by the participants in real time: (1) individuals propose breakout groups; (2) everyone signs up for one (or more) groups; (3) the groups with the most interested parties then meet, with reports from each group presented and discussed in a subsequent plenary session.


Robbins has been engaged with photography and design since the 1960s, when he worked for a professional photography laboratory. He now prefers digital photography and tools for their precision and reproducibility. He designed his first web site more than 20 years ago and he personally designed and implemented this web site. He engages in graphic design as a hobby.

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E-mail: RJR8222@gmail.com

Collection of publications by R J Robbins

Reprints and preprints of publications, slide presentations, instructional materials, and data compilations written or prepared by Robert Robbins. Most papers deal with computational biology, genome informatics, using information technology to support biomedical research, and related matters.

Research Gate page for R J Robbins

ResearchGate is a social networking site for scientists and researchers to share papers, ask and answer questions, and find collaborators. According to a study by Nature and an article in Times Higher Education , it is the largest academic social network in terms of active users.

Curriculum Vitae for R J Robbins

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Curriculum Vitae for R J Robbins

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RJR Picks from Around the Web (updated 11 MAY 2018 )