101
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Marttinen P, Croucher NJ, Gutmann MU, Corander J, Hanage WP. Recombination produces coherent bacterial species clusters in both core and accessory genomes. Microb Genom 2015; 1:e000038. [PMID: 28348822 PMCID: PMC5320679 DOI: 10.1099/mgen.0.000038] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 10/06/2015] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Population samples show bacterial genomes can be divided into a core of ubiquitous genes and accessory genes that are present in a fraction of isolates. The ecological significance of this variation in gene content remains unclear. However, microbiologists agree that a bacterial species should be 'genomically coherent', even though there is no consensus on how this should be determined. RESULTS We use a parsimonious model combining diversification in both the core and accessory genome, including mutation, homologous recombination (HR) and horizontal gene transfer (HGT) introducing new loci, to produce a population of interacting clusters of strains with varying genome content. New loci introduced by HGT may then be transferred on by HR. The model fits well to a systematic population sample of 616 pneumococcal genomes, capturing the major features of the population structure with parameter values that agree well with empirical estimates. CONCLUSIONS The model does not include explicit selection on individual genes, suggesting that crude comparisons of gene content may be a poor predictor of ecological function. We identify a clearly divergent subpopulation of pneumococci that are inconsistent with the model and may be considered genomically incoherent with the rest of the population. These strains have a distinct disease tropism and may be rationally defined as a separate species. We also find deviations from the model that may be explained by recent population bottlenecks or spatial structure.
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Affiliation(s)
- Pekka Marttinen
- Aalto University, Espoo, Finland
- Center for Communicable Disease Dynamics, Harvard School of Public Health, Boston, MA, USA
| | | | | | | | - William P. Hanage
- Center for Communicable Disease Dynamics, Harvard School of Public Health, Boston, MA, USA
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102
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Reuter S, Corander J, de Been M, Harris S, Cheng L, Hall M, Thomson NR, McNally A. Directional gene flow and ecological separation in Yersinia enterocolitica. Microb Genom 2015; 1:e000030. [PMID: 28348815 PMCID: PMC5320568 DOI: 10.1099/mgen.0.000030] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Accepted: 08/09/2015] [Indexed: 01/07/2023] Open
Abstract
Yersinia enterocolitica is a common cause of food-borne gastroenteritis worldwide. Recent work defining the phylogeny of the genus Yersinia subdivided Y. enterocolitica into six distinct phylogroups. Here, we provide detailed analyses of the evolutionary processes leading to the emergence of these phylogroups. The dominant phylogroups isolated from human infections, PG3–5, show very little diversity at the sequence level, but do present marked patterns of gain and loss of functions, including those involved in pathogenicity and metabolism, including the acquisition of phylogroup-specific O-antigen loci. We tracked gene flow across the species in the core and accessory genome, and show that the non-pathogenic PG1 strains act as a reservoir for diversity, frequently acting as donors in recombination events. Analysis of the core and accessory genome also suggested that the different Y. enterocolitica phylogroups may be ecologically separated, in contrast to the long-held belief of common shared ecological niches across the Y. enterocolitica species.
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Affiliation(s)
- Sandra Reuter
- Pathogen Genomics, Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1SA, UK.,Pathogen Research Group, Nottingham Trent University, Nottingham NG11 8NS, UK
| | - Jukka Corander
- Department of Mathematics and Statistics, University of Helsinki, Helsinki, Finland
| | - Mark de Been
- Department of Medical Microbiology, University Medical Centre Utrecht, Utrecht, Netherlands
| | - Simon Harris
- Pathogen Genomics, Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1SA, UK
| | - Lu Cheng
- Department of Mathematics and Statistics, University of Helsinki, Helsinki, Finland
| | - Miquette Hall
- Pathogen Research Group, Nottingham Trent University, Nottingham NG11 8NS, UK
| | - Nicholas R Thomson
- Pathogen Genomics, Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1SA, UK.,Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
| | - Alan McNally
- Pathogen Research Group, Nottingham Trent University, Nottingham NG11 8NS, UK
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103
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Christian N, Whitaker BK, Clay K. Microbiomes: unifying animal and plant systems through the lens of community ecology theory. Front Microbiol 2015; 6:869. [PMID: 26441846 PMCID: PMC4561359 DOI: 10.3389/fmicb.2015.00869] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 08/10/2015] [Indexed: 12/20/2022] Open
Abstract
The field of microbiome research is arguably one of the fastest growing in biology. Bacteria feature prominently in studies on animal health, but fungi appear to be the more prominent functional symbionts for plants. Despite the similarities in the ecological organization and evolutionary importance of animal-bacterial and plant-fungal microbiomes, there is a general failure across disciplines to integrate the advances made in each system. Researchers studying bacterial symbionts in animals benefit from greater access to efficient sequencing pipelines and taxonomic reference databases, perhaps due to high medical and veterinary interest. However, researchers studying plant-fungal symbionts benefit from the relative tractability of fungi under laboratory conditions and ease of cultivation. Thus each system has strengths to offer, but both suffer from the lack of a common conceptual framework. We argue that community ecology best illuminates complex species interactions across space and time. In this synthesis we compare and contrast the animal-bacterial and plant-fungal microbiomes using six core theories in community ecology (i.e., succession, community assembly, metacommunities, multi-trophic interactions, disturbance, restoration). The examples and questions raised are meant to spark discussion amongst biologists and lead to the integration of these two systems, as well as more informative, manipulatory experiments on microbiomes research.
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Affiliation(s)
- Natalie Christian
- *Correspondence: Natalie Christian and Briana K. Whitaker, Evolution, Ecology and Behavior Program, Department of Biology, Indiana University, Jordan Hall, 1001 East 3rd Street, Bloomington, IN 47405, USA, ;
| | - Briana K. Whitaker
- *Correspondence: Natalie Christian and Briana K. Whitaker, Evolution, Ecology and Behavior Program, Department of Biology, Indiana University, Jordan Hall, 1001 East 3rd Street, Bloomington, IN 47405, USA, ;
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104
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Krause DJ, Whitaker RJ. Inferring Speciation Processes from Patterns of Natural Variation in Microbial Genomes. Syst Biol 2015; 64:926-35. [PMID: 26316424 PMCID: PMC4604833 DOI: 10.1093/sysbio/syv050] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 06/09/2015] [Indexed: 01/22/2023] Open
Abstract
Microbial species concepts have long been the focus of contentious debate, fueled by technological limitations to the genetic resolution of species, by the daunting task of investigating phenotypic variation among individual microscopic organisms, and by a lack of understanding of gene flow in reproductively asexual organisms that are prone to promiscuous horizontal gene transfer. Population genomics, the emerging approach of analyzing the complete genomes of a multitude of closely related organisms, is poised to overcome these limitations by providing a window into patterns of genome variation revealing the evolutionary processes through which species diverge. This new approach is more than just an extension of previous multilocus sequencing technologies, in that it provides a comprehensive view of interacting evolutionary processes. Here we argue that the application of population genomic tools in a rigorous population genetic framework will help to identify the processes of microbial speciation and ultimately lead to a general species concept based on the unique biology and ecology of microorganisms.
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Affiliation(s)
- David J Krause
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Rachel J Whitaker
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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105
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Abstract
SUMMARY Members of the Roseobacter clade are equipped with a tremendous diversity of metabolic capabilities, which in part explains their success in so many different marine habitats. Ideas on how this diversity evolved and is maintained are reviewed, focusing on recent evolutionary studies exploring the timing and mechanisms of Roseobacter ecological diversification.
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106
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Lawson CE, Strachan BJ, Hanson NW, Hahn AS, Hall ER, Rabinowitz B, Mavinic DS, Ramey WD, Hallam SJ. Rare taxa have potential to make metabolic contributions in enhanced biological phosphorus removal ecosystems. Environ Microbiol 2015; 17:4979-93. [PMID: 25857222 DOI: 10.1111/1462-2920.12875] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 04/06/2015] [Accepted: 04/06/2015] [Indexed: 12/01/2022]
Abstract
Enhanced biological phosphorus removal (EBPR) relies on diverse but specialized microbial communities to mediate the cycling and ultimate removal of phosphorus from municipal wastewaters. However, little is known about microbial activity and dynamics in relation to process fluctuations in EBPR ecosystems. Here, we monitored temporal changes in microbial community structure and potential activity across each bioreactor zone in a pilot-scale EBPR treatment plant by examining the ratio of small subunit ribosomal RNA (SSU rRNA) to SSU rRNA gene (rDNA) over a 120 day study period. Although the majority of operational taxonomic units (OTUs) in the EBPR ecosystem were rare, many maintained high potential activities based on SSU rRNA : rDNA ratios, suggesting that rare OTUs contribute substantially to protein synthesis potential in EBPR ecosystems. Few significant differences in OTU abundance and activity were observed between bioreactor redox zones, although differences in temporal activity were observed among phylogenetically cohesive OTUs. Moreover, observed temporal activity patterns could not be explained by measured process parameters, suggesting that other ecological drivers, such as grazing or viral lysis, modulated community interactions. Taken together, these results point towards complex interactions selected for within the EBPR ecosystem and highlight a previously unrecognized functional potential among low abundance microorganisms in engineered ecosystems.
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Affiliation(s)
- Christopher E Lawson
- Department of Civil Engineering, University of British Columbia, Vancouver, BC, Canada
| | - Blake J Strachan
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Niels W Hanson
- Graduate Program in Bioinformatics, University of British Columbia, Vancouver, BC, Canada
| | - Aria S Hahn
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Eric R Hall
- Department of Civil Engineering, University of British Columbia, Vancouver, BC, Canada
| | - Barry Rabinowitz
- Department of Civil Engineering, University of British Columbia, Vancouver, BC, Canada.,CH2M Hill Canada, 4720 Kingsway Suite 2100, Burnaby, BC, Canada
| | - Donald S Mavinic
- Department of Civil Engineering, University of British Columbia, Vancouver, BC, Canada
| | - William D Ramey
- Department of Civil Engineering, University of British Columbia, Vancouver, BC, Canada.,Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Steven J Hallam
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada.,Graduate Program in Bioinformatics, University of British Columbia, Vancouver, BC, Canada
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107
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Non-symbiotic Bradyrhizobium ecotypes dominate North American forest soils. ISME JOURNAL 2015; 9:2435-41. [PMID: 25909973 DOI: 10.1038/ismej.2015.54] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Revised: 02/27/2015] [Accepted: 03/03/2015] [Indexed: 11/08/2022]
Abstract
The genus Bradyrhizobium has served as a model system for studying host-microbe symbiotic interactions and nitrogen fixation due to its importance in agricultural productivity and global nitrogen cycling. In this study, we identify a bacterial group affiliated with this genus that dominates the microbial communities of coniferous forest soils from six distinct ecozones across North America. Representative isolates from this group were obtained and characterized. Using quantitative population genomics, we show that forest soil populations of Bradyrhizobium represent ecotypes incapable of nodulating legume root hairs or fixing atmospheric nitrogen. Instead, these populations appear to be free living and have a greater potential for metabolizing aromatic carbon sources than their close symbiotic relatives. In addition, we identify fine-scaled differentiation between populations inhabiting neighboring soil layers that illustrate how diversity within Bradyrhizobium is structured by habitat similarity. These findings reconcile incongruent observations about this widely studied and important group of bacteria and highlight the value of ecological context to interpretations of microbial diversity and taxonomy. These results further suggest that the influence of this genus likely extends well beyond facilitating agriculture, especially as forest ecosystems are large and integral components of the biosphere. In addition, this study demonstrates how focusing research on economically important microorganisms can bias our understanding of the natural world.
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108
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Takeuchi N, Cordero OX, Koonin EV, Kaneko K. Gene-specific selective sweeps in bacteria and archaea caused by negative frequency-dependent selection. BMC Biol 2015; 13:20. [PMID: 25928466 PMCID: PMC4410459 DOI: 10.1186/s12915-015-0131-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Accepted: 03/13/2015] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Fixation of beneficial genes in bacteria and archaea (collectively, prokaryotes) is often believed to erase pre-existing genomic diversity through the hitchhiking effect, a phenomenon known as genome-wide selective sweep. Recent studies, however, indicate that beneficial genes spread through a prokaryotic population via recombination without causing genome-wide selective sweeps. These gene-specific selective sweeps seem to be at odds with the existing estimates of recombination rates in prokaryotes, which appear far too low to explain such phenomena. RESULTS We use mathematical modeling to investigate potential solutions to this apparent paradox. Most microbes in nature evolve in heterogeneous, dynamic communities, in which ecological interactions can substantially impact evolution. Here, we focus on the effect of negative frequency-dependent selection (NFDS) such as caused by viral predation (kill-the-winner dynamics). The NFDS maintains multiple genotypes within a population, so that a gene beneficial to every individual would have to spread via recombination, hence a gene-specific selective sweep. However, gene loci affected by NFDS often are located in variable regions of microbial genomes that contain genes involved in the mobility of selfish genetic elements, such as integrases or transposases. Thus, the NFDS-affected loci are likely to experience elevated rates of recombination compared with the other loci. Consequently, these loci might be effectively unlinked from the rest of the genome, so that NFDS would be unable to prevent genome-wide selective sweeps. To address this problem, we analyzed population genetic models of selective sweeps in prokaryotes under NFDS. The results indicate that NFDS can cause gene-specific selective sweeps despite the effect of locally elevated recombination rates, provided NFDS affects more than one locus and the basal rate of recombination is sufficiently low. Although these conditions might seem to contradict the intuition that gene-specific selective sweeps require high recombination rates, they actually decrease the effective rate of recombination at loci affected by NFDS relative to the per-locus basal level, so that NFDS can cause gene-specific selective sweeps. CONCLUSION Because many free-living prokaryotes are likely to evolve under NFDS caused by ubiquitous viruses, gene-specific selective sweeps driven by NFDS are expected to be a major, general phenomenon in prokaryotic populations.
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Affiliation(s)
- Nobuto Takeuchi
- Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan.
| | - Otto X Cordero
- Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland.
| | - Eugene V Koonin
- National Institutes of Health, National Library of Medicine, National Center for Biotechnology Information, Bethesda, USA.
| | - Kunihiko Kaneko
- Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan.
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109
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110
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Genomic and phenotypic differentiation among Methanosarcina mazei populations from Columbia River sediment. ISME JOURNAL 2015; 9:2191-205. [PMID: 25756680 DOI: 10.1038/ismej.2015.31] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Revised: 01/08/2015] [Accepted: 01/28/2015] [Indexed: 11/09/2022]
Abstract
Methanogenic archaea are genotypically and phenotypically diverse organisms that are integral to carbon cycling in anaerobic environments. Owing to their genetic tractability and ability to be readily cultivated, Methanosarcina spp. have become a powerful model system for understanding methanogen biology at the cellular systems level. However, relatively little is known of how genotypic and phenotypic variation is partitioned in Methanosarcina populations inhabiting natural environments and the possible ecological and evolutionary implications of such variation. Here, we have identified how genomic and phenotypic diversity is partitioned within and between Methanosarcina mazei populations obtained from two different sediment environments in the Columbia River Estuary (Oregon, USA). Population genomic analysis of 56 M. mazei isolates averaging <1% nucleotide divergence revealed two distinct clades, which we refer to as 'mazei-T' and 'mazei-WC'. Genomic analyses showed that these clades differed in gene content and fixation of allelic variants, which point to potential differences in primary metabolism and also interactions with foreign genetic elements. This hypothesis of niche partitioning was supported by laboratory growth experiments that revealed significant differences in trimethylamine utilization. These findings improve our understanding of the ecologically relevant scales of genomic variation in natural systems and demonstrate interactions between genetic and ecological diversity in these easily cultivable and genetically tractable model methanogens.
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111
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Abstract
Recent advances in studying the dynamics of marine microbial communities have shown that the composition of these communities follows predictable patterns and involves complex network interactions, which shed light on the underlying processes regulating these globally important organisms. Such 'holistic' (or organism- and system-based) studies of these communities complement popular reductionist, often culture-based, approaches for understanding organism function one gene or protein at a time. In this Review, we summarize our current understanding of marine microbial community dynamics at various scales, from hours to decades. We also explain how the data illustrate community resilience and seasonality, and reveal interactions among microorganisms.
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112
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Kirkup BC. Bacterial Strain Diversity Within Wounds. Adv Wound Care (New Rochelle) 2015; 4:12-23. [PMID: 25566411 DOI: 10.1089/wound.2014.0560] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 06/23/2014] [Indexed: 12/17/2022] Open
Abstract
Significance: Rare bacterial taxa (taxa of low relative frequency) are numerous and ubiquitous in virtually any sample-including wound samples. In addition, even the high-frequency genera and species contain multiple strains. These strains, individually, are each only a small fraction of the total bacterial population. Against the view that wounds contain relatively few kinds of bacteria, this newly recognized diversity implies a relatively high rate of migration into the wound and the potential for diversification during infection. Understanding the biological and medical importance of these numerous taxa is an important new element of wound microbiology. Recent Advances: Only recently have these numerous strains been discovered; the technology to detect, identify, and characterize them is still in its infancy. Multiple strains of both gram-negative and gram-positive bacteria have been found in a single wound. In the few cases studied, the distribution of the bacteria suggests microhabitats and biological interactions. Critical Issues: The distribution of the strains, their phenotypic diversity, and their interactions are still largely uncharacterized. The technologies to investigate this level of genomic detail are still developing and have not been largely deployed to investigate wounds. Future Directions: As advanced metagenomics, single-cell genomics, and advanced microscopy develop, the study of wound microbiology will better address the complex interplay of numerous individually rare strains with both the host and each other.
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Affiliation(s)
- Benjamin C. Kirkup
- FE Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland
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113
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Microbial taxonomy in the post-genomic era: rebuilding from scratch? Arch Microbiol 2014; 197:359-70. [PMID: 25533848 DOI: 10.1007/s00203-014-1071-2] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Revised: 12/04/2014] [Accepted: 12/05/2014] [Indexed: 12/20/2022]
Abstract
Microbial taxonomy should provide adequate descriptions of bacterial, archaeal, and eukaryotic microbial diversity in ecological, clinical, and industrial environments. Its cornerstone, the prokaryote species has been re-evaluated twice. It is time to revisit polyphasic taxonomy, its principles, and its practice, including its underlying pragmatic species concept. Ultimately, we will be able to realize an old dream of our predecessor taxonomists and build a genomic-based microbial taxonomy, using standardized and automated curation of high-quality complete genome sequences as the new gold standard.
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114
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Urbanczyk H, Ogura Y, Hayashi T. Contrasting inter- and intraspecies recombination patterns in the "Harveyi clade" vibrio collected over large spatial and temporal scales. Genome Biol Evol 2014; 7:71-80. [PMID: 25527835 PMCID: PMC4316622 DOI: 10.1093/gbe/evu269] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Recombination plays an important role in the divergence of bacteria, but the frequency of interspecies and intraspecies recombination events remains poorly understood. We investigated recombination events that occurred within core genomes of 35 Vibrio strains (family Vibrionaceae, Gammaproteobacteria), from six closely related species in the so-called “Harveyi clade.” The strains were selected from a collection of strains isolated in the last 90 years, from various environments worldwide. We found a close relationship between the number of interspecies recombination events within core genomes of the 35 strains and the overall genomic identity, as inferred from calculations of the average nucleotide identity. The relationship between the overall nucleotide identity and the number of detected interspecies recombination events was comparable when analyzing strains isolated over 80 years apart, from different hemispheres, or from different ecologies, as well as in strains isolated from the same geographic location within a short time frame. We further applied the same method of detecting recombination events to analyze 11 strains of Vibrio campbellii, and identified disproportionally high number of intraspecies recombination events within the core genomes of some, but not all, strains. The high number of recombination events was detected between V. campbellii strains that have significant temporal (over 18 years) and geographical (over 10,000 km) differences in their origins of isolation. Results of this study reveal a remarkable stability of Harveyi clade species, and give clues about the origins and persistence of species in the clade.
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Affiliation(s)
- Henryk Urbanczyk
- Department of Marine Biology and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, Japan
| | - Yoshitoshi Ogura
- Division of Microbial Genomics, Department of Genomics and Bioenvironmental Science, Frontier Science Research Center, University of Miyazaki, Japan Division of Microbiology, Department of Infectious Diseases, Faculty of Medicine, University of Miyazaki, Japan
| | - Tetsuya Hayashi
- Division of Microbial Genomics, Department of Genomics and Bioenvironmental Science, Frontier Science Research Center, University of Miyazaki, Japan Division of Microbiology, Department of Infectious Diseases, Faculty of Medicine, University of Miyazaki, Japan
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115
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Avitia M, Escalante AE, Rebollar EA, Moreno-Letelier A, Eguiarte LE, Souza V. Population expansions shared among coexisting bacterial lineages are revealed by genetic evidence. PeerJ 2014; 2:e696. [PMID: 25548732 PMCID: PMC4273935 DOI: 10.7717/peerj.696] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 11/22/2014] [Indexed: 01/19/2023] Open
Abstract
Comparative population studies can help elucidate the influence of historical events upon current patterns of biodiversity among taxa that coexist in a given geographic area. In particular, comparative assessments derived from population genetics and coalescent theory have been used to investigate population dynamics of bacterial pathogens in order to understand disease epidemics. In contrast, and despite the ecological relevance of non-host associated and naturally occurring bacteria, there is little understanding of the processes determining their diversity. Here we analyzed the patterns of genetic diversity in coexisting populations of three genera of bacteria (Bacillus, Exiguobacterium, and Pseudomonas) that are abundant in the aquatic systems of the Cuatro Cienegas Basin, Mexico. We tested the hypothesis that a common habitat leaves a signature upon the genetic variation present in bacterial populations, independent of phylogenetic relationships. We used multilocus markers to assess genetic diversity and (1) performed comparative phylogenetic analyses, (2) described the genetic structure of bacterial populations, (3) calculated descriptive parameters of genetic diversity, (4) performed neutrality tests, and (5) conducted coalescent-based historical reconstructions. Our results show a trend of synchronic expansions across most populations independent of both lineage and sampling site. Thus, we provide empirical evidence supporting the analysis of coexisting bacterial lineages in natural environments to advance our understanding of bacterial evolution beyond medical or health-related microbes.
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Affiliation(s)
- Morena Avitia
- Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México , México DF , México
| | - Ana E Escalante
- Departamento de Ecología de la Biodiversidad, Laboratorio Nacional de Ciencias de la Sostenibilidad, Instituto de Ecología, Universidad Nacional Autónoma de México , México DF , México
| | - Eria A Rebollar
- Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México , México DF , México ; Biology Department, James Madison University , Harrisonburg VA , USA
| | | | - Luis E Eguiarte
- Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México , México DF , México
| | - Valeria Souza
- Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México , México DF , México
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116
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Nesbø CL, S Swithers K, Dahle H, Haverkamp THA, Birkeland NK, Sokolova T, Kublanov I, Zhaxybayeva O. Evidence for extensive gene flow and Thermotoga subpopulations in subsurface and marine environments. ISME JOURNAL 2014; 9:1532-42. [PMID: 25500512 DOI: 10.1038/ismej.2014.238] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 11/03/2014] [Accepted: 11/10/2014] [Indexed: 11/09/2022]
Abstract
Oil reservoirs represent a nutrient-rich ecological niche of the deep biosphere. Although most oil reservoirs are occupied by microbial populations, when and how the microbes colonized these environments remains unanswered. To address this question, we compared 11 genomes of Thermotoga maritima-like hyperthermophilic bacteria from two environment types: subsurface oil reservoirs in the North Sea and Japan, and marine sites located in the Kuril Islands, Italy and the Azores. We complemented our genomes with Thermotoga DNA from publicly available subsurface metagenomes from North America and Australia. Our analysis revealed complex non-bifurcating evolutionary history of the isolates' genomes, suggesting high amounts of gene flow across all sampled locations, a conjecture supported by numerous recombination events. Genomes from the same type of environment tend to be more similar, and have exchanged more genes with each other than with geographically close isolates from different types of environments. Hence, Thermotoga populations of oil reservoirs do not appear isolated, a requirement of the 'burial and isolation' hypothesis, under which reservoir bacteria are descendants of the isolated communities buried with sediments that over time became oil reservoirs. Instead, our analysis supports a more complex view, where bacteria from subsurface and marine populations have been continuously migrating into the oil reservoirs and influencing their genetic composition. The Thermotoga spp. in the oil reservoirs in the North Sea and Japan probably entered the reservoirs shortly after they were formed. An Australian oil reservoir, on the other hand, was likely colonized very recently, perhaps during human reservoir development.
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Affiliation(s)
- Camilla L Nesbø
- 1] Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, Blindern, Oslo, Norway [2] Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Kristen S Swithers
- 1] Department of Cell Biology, Yale School of Medicine, Yale University, New Haven, CT, USA [2] Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, USA
| | - Håkon Dahle
- Department of Biology and Centre for Geobiology, University of Bergen, Bergen, Norway
| | - Thomas H A Haverkamp
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, Blindern, Oslo, Norway
| | - Nils-Kåre Birkeland
- Department of Biology and Centre for Geobiology, University of Bergen, Bergen, Norway
| | - Tatiana Sokolova
- Winogradsky Institute of Microbiology, Russian Academy of Sciences, Moscow, Russia
| | - Ilya Kublanov
- Winogradsky Institute of Microbiology, Russian Academy of Sciences, Moscow, Russia
| | - Olga Zhaxybayeva
- 1] Department of Biological Sciences, Dartmouth College, Hanover, NH, USA [2] Department of Computer Science, Dartmouth College, Hanover, NH, USA
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