1
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Yu D, Stothard P, Neumann NF. Emergence of potentially disinfection-resistant, naturalized Escherichia coli populations across food- and water-associated engineered environments. Sci Rep 2024; 14:13478. [PMID: 38866876 PMCID: PMC11169474 DOI: 10.1038/s41598-024-64241-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Accepted: 06/06/2024] [Indexed: 06/14/2024] Open
Abstract
The Escherichia coli species is comprised of several 'ecotypes' inhabiting a wide range of host and natural environmental niches. Recent studies have suggested that novel naturalized ecotypes have emerged across wastewater treatment plants and meat processing facilities. Phylogenetic and multilocus sequence typing analyses clustered naturalized wastewater and meat plant E. coli strains into two main monophyletic clusters corresponding to the ST635 and ST399 sequence types, with several serotypes identified by serotyping, potentially representing distinct lineages that have naturalized across wastewater treatment plants and meat processing facilities. This evidence, taken alongside ecotype prediction analyses that distinguished the naturalized strains from their host-associated counterparts, suggests these strains may collectively represent a novel ecotype that has recently emerged across food- and water-associated engineered environments. Interestingly, pan-genomic analyses revealed that the naturalized strains exhibited an abundance of biofilm formation, defense, and disinfection-related stress resistance genes, but lacked various virulence and colonization genes, indicating that their naturalization has come at the cost of fitness in the original host environment.
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Affiliation(s)
- Daniel Yu
- School of Public Health, University of Alberta, Edmonton, AB, Canada.
- Antimicrobial Resistance-One Health Consortium, Calgary, AB, Canada.
| | - Paul Stothard
- Department of Agriculture, Food and Nutritional Sciences, University of Alberta, Edmonton, AB, Canada
| | - Norman F Neumann
- School of Public Health, University of Alberta, Edmonton, AB, Canada
- Antimicrobial Resistance-One Health Consortium, Calgary, AB, Canada
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2
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Morel-Letelier I, Yuen B, Kück AC, Camacho-García YE, Petersen JM, Lara M, Leray M, Eisen JA, Osvatic JT, Gros O, Wilkins LGE. Adaptations to nitrogen availability drive ecological divergence of chemosynthetic symbionts. PLoS Genet 2024; 20:e1011295. [PMID: 38820540 PMCID: PMC11168628 DOI: 10.1371/journal.pgen.1011295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 06/12/2024] [Accepted: 05/08/2024] [Indexed: 06/02/2024] Open
Abstract
Bacterial symbionts, with their shorter generation times and capacity for horizontal gene transfer (HGT), play a critical role in allowing marine organisms to cope with environmental change. The closure of the Isthmus of Panama created distinct environmental conditions in the Tropical Eastern Pacific (TEP) and Caribbean, offering a "natural experiment" for studying how closely related animals evolve and adapt under environmental change. However, the role of bacterial symbionts in this process is often overlooked. We sequenced the genomes of endosymbiotic bacteria in two sets of sister species of chemosymbiotic bivalves from the genera Codakia and Ctena (family Lucinidae) collected on either side of the Isthmus, to investigate how differing environmental conditions have influenced the selection of symbionts and their metabolic capabilities. The lucinid sister species hosted different Candidatus Thiodiazotropha symbionts and only those from the Caribbean had the genetic potential for nitrogen fixation, while those from the TEP did not. Interestingly, this nitrogen-fixing ability did not correspond to symbiont phylogeny, suggesting convergent evolution of nitrogen fixation potential under nutrient-poor conditions. Reconstructing the evolutionary history of the nifHDKT operon by including other lucinid symbiont genomes from around the world further revealed that the last common ancestor (LCA) of Ca. Thiodiazotropha lacked nif genes, and populations in oligotrophic habitats later re-acquired the nif operon through HGT from the Sedimenticola symbiont lineage. Our study suggests that HGT of the nif operon has facilitated niche diversification of the globally distributed Ca. Thiodiazotropha endolucinida species clade. It highlights the importance of nitrogen availability in driving the ecological diversification of chemosynthetic symbiont species and the role that bacterial symbionts may play in the adaptation of marine organisms to changing environmental conditions.
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Affiliation(s)
- Isidora Morel-Letelier
- Eco-Evolutionary Interactions Group, Max Planck Institute for Marine Microbiology (MPIMM), Bremen, Germany
| | - Benedict Yuen
- Eco-Evolutionary Interactions Group, Max Planck Institute for Marine Microbiology (MPIMM), Bremen, Germany
| | - A. Carlotta Kück
- Eco-Evolutionary Interactions Group, Max Planck Institute for Marine Microbiology (MPIMM), Bremen, Germany
| | - Yolanda E. Camacho-García
- Centro de Investigación en Ciencias del Mar y Limnología (CIMAR), Universidad de Costa Rica, San Pedro, San José, Costa Rica
- Centro de Investigación en Biodiversidad y Ecología Tropical (CIBET), Universidad de Costa Rica, San Pedro, San José, Costa Rica
- Escuela de Biología, Universidad de Costa Rica, San Pedro, San José, Costa Rica
| | - Jillian M. Petersen
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | - Minor Lara
- Diving Center Cuajiniquil, Provincia de Guanacaste, Cuajiniquil, Costa Rica
| | - Matthieu Leray
- Smithsonian Tropical Research Institute, Balboa, Ancon, Republic of Panamá
| | - Jonathan A. Eisen
- Department of Evolution and Ecology, University of California, Davis, Davis, California, United States of America
- Department of Medical Microbiology and Immunology, University of California, Davis, Davis, California, United States of America
| | - Jay T. Osvatic
- Joint Microbiome Facility of the Medical University of Vienna and the University of Vienna, Vienna, Austria
- Department of Laboratory Medicine, Medical University of Vienna, Vienna, Austria
| | - Olivier Gros
- Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum National d’Histoire Naturelle, CNRS, Sorbonne Université, Université des Antilles, Pointe-à-Pitre, France
| | - Laetitia G. E. Wilkins
- Eco-Evolutionary Interactions Group, Max Planck Institute for Marine Microbiology (MPIMM), Bremen, Germany
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3
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Robicheau BM, Tolman J, Desai D, LaRoche J. Microevolutionary patterns in ecotypes of the symbiotic cyanobacterium UCYN-A revealed from a Northwest Atlantic coastal time series. SCIENCE ADVANCES 2023; 9:eadh9768. [PMID: 37774025 PMCID: PMC10541017 DOI: 10.1126/sciadv.adh9768] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Accepted: 08/28/2023] [Indexed: 10/01/2023]
Abstract
UCYN-A is a globally important nitrogen-fixing symbiotic microbe often found in colder regions and coastal areas where nitrogen fixation has been overlooked. We present a 3-year coastal Northwest Atlantic time series of UCYN-A by integrating oceanographic data with weekly nifH and16S rRNA gene sequencing and quantitative PCR assays for UCYN-A ecotypes. High UCYN-A relative abundances dominated by A1 to A4 ecotypes reoccurred annually in the coastal Northwest Atlantic. Although UCYN-A was detected every summer/fall, the ability to observe separate ecotypes may be highly dependent on sampling time given intense interannual and weekly variability of ecotype-specific occurrences. Additionally, much of UCYN-A's rarer diversity was populated by short-lived neutral mutational variants, therefore providing insight into UCYN-A's microevolutionary patterns. For instance, rare ASVs exhibited community composition restructuring annually, while also sharing a common connection to a dominant ASV within each ecotype. Our study provides additional perspectives for interpreting UCYN-A intraspecific diversity and underscores the need for high-resolution datasets when deciphering spatiotemporal ecologies within UCYN-A.
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Affiliation(s)
- Brent M. Robicheau
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Jennifer Tolman
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Dhwani Desai
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
- Integrated Microbiome Resource, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Julie LaRoche
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
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4
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Tominaga K, Ogawa-Haruki N, Nishimura Y, Watai H, Yamamoto K, Ogata H, Yoshida T. Prevalence of Viral Frequency-Dependent Infection in Coastal Marine Prokaryotes Revealed Using Monthly Time Series Virome Analysis. mSystems 2023; 8:e0093122. [PMID: 36722950 PMCID: PMC9948707 DOI: 10.1128/msystems.00931-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 12/29/2022] [Indexed: 02/02/2023] Open
Abstract
Viruses infecting marine prokaryotes have a large impact on the diversity and dynamics of their hosts. Model systems suggest that viral infection is frequency dependent and constrained by the virus-host encounter rate. However, it is unclear whether frequency-dependent infection is pervasive among the abundant prokaryotic populations with different temporal dynamics. To address this question, we performed a comparison of prokaryotic and viral communities using 16S rRNA amplicon and virome sequencing based on samples collected monthly for 2 years at a Japanese coastal site, Osaka Bay. Concurrent seasonal shifts observed in prokaryotic and viral community dynamics indicated that the abundance of viruses correlated with that of their predicted host phyla (or classes). Cooccurrence network analysis between abundant prokaryotes and viruses revealed 6,423 cooccurring pairs, suggesting a tight coupling of host and viral abundances and their "one-to-many" correspondence. Although stable dominant species, such as SAR11, showed few cooccurring viruses, a fast succession of their viruses suggests that viruses infecting these populations changed continuously. Our results suggest that frequency-dependent viral infection prevails in coastal marine prokaryotes regardless of host taxa and temporal dynamics. IMPORTANCE There is little room for doubt that viral infection is prevalent among abundant marine prokaryotes regardless of their taxa or growth strategy. However, comprehensive evaluations of viral infections in natural prokaryotic communities are still technically difficult. In this study, we examined viral infection in abundant prokaryotes by monitoring the monthly dynamics of prokaryotic and viral communities at a eutrophic coastal site, Osaka Bay. We compared the community dynamics of viruses with those of their putative hosts based on genome-based in silico host prediction. We observed frequent cooccurrence among the predicted virus-host pairs, suggesting that viral infection is prevalent in abundant prokaryotes regardless of their taxa or temporal dynamics. This likely indicates that frequent lysis of the abundant prokaryotes via viral infection has a considerable contribution to the biogeochemical cycling and maintenance of prokaryotic community diversity.
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Affiliation(s)
- Kento Tominaga
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
- Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, Japan
| | | | - Yosuke Nishimura
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Kanagawa, Japan
| | - Hiroyasu Watai
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Keigo Yamamoto
- Research Institute of Environment, Agriculture and Fisheries, Osaka Prefecture, Osaka, Japan
| | - Hiroyuki Ogata
- Institute for Chemical Research, Kyoto University, Kyoto, Japan
| | - Takashi Yoshida
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
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5
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Genome-Centric Dynamics Shape the Diversity of Oral Bacterial Populations. mBio 2022; 13:e0241422. [PMID: 36214570 PMCID: PMC9765137 DOI: 10.1128/mbio.02414-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Two major viewpoints have been put forward for how microbial populations change, differing in whether adaptation is driven principally by gene-centric or genome-centric processes. Longitudinal sampling at microbially relevant timescales, i.e., days to weeks, is critical for distinguishing these mechanisms. Because of its significance for both microbial ecology and human health and its accessibility and high level of curation, we used the oral microbiota to study bacterial intrapopulation genome dynamics. Metagenomes were generated by shotgun sequencing of total community DNA from the healthy tongues of 17 volunteers at four to seven time points obtained over intervals of days to weeks. We obtained 390 high-quality metagenome-assembled genomes (MAGs) defining population genomes from 55 genera. The vast majority of genes in each MAG were tightly linked over the 2-week sampling window, indicating that the majority of the population's genomes were temporally stable at the MAG level. MAG-defined populations were composed of up to 5 strains, as determined by single-nucleotide-variant frequencies. Although most were stable over time, individual strains carrying over 100 distinct genes that rose from low abundance to dominance in a population over a period of days were detected. These results indicate a genome-wide as opposed to a gene-level process of population change. We infer that genome-wide selection of ecotypes is the dominant mode of adaptation in the oral populations over short timescales. IMPORTANCE The oral microbiome represents a microbial community of critical relevance to human health. Recent studies have documented the diversity and dynamics of different bacteria to reveal a rich, stable ecosystem characterized by strain-level dynamics. However, bacterial populations and their genomes are neither monolithic nor static; their genomes are constantly evolving to lose, gain, or alter their functional potential. To better understand how microbial genomes change in complex communities, we used culture-independent approaches to reconstruct the genomes (MAGs) for bacterial populations that approximated different species, in 17 healthy donors' mouths over a 2-week window. Our results underscored the importance of strain-level dynamics, which agrees with and expands on the conclusions of previous research. Altogether, these observations reveal patterns of genomic dynamics among strains of oral bacteria occurring over a matter of days.
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6
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Liu Y, Cui X, Yang R, Zhang Y, Xu Y, Liu G, Zhang B, Wang J, Wang X, Zhang W, Chen T, Zhang G. Genomic Insights into the Radiation-Resistant Capability of Sphingomonas qomolangmaensis S5-59 T and Sphingomonas glaciei S8-45 T, Two Novel Bacteria from the North Slope of Mount Everest. Microorganisms 2022; 10:microorganisms10102037. [PMID: 36296313 PMCID: PMC9611098 DOI: 10.3390/microorganisms10102037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 10/10/2022] [Accepted: 10/12/2022] [Indexed: 11/07/2022] Open
Abstract
Mount Everest provides natural advantages to finding radiation-resistant extremophiles that are functionally mechanistic and possess commercial significance. (1) Background: Two bacterial strains, designated S5-59T and S8-45T, were isolated from moraine samples collected from the north slope of Mount Everest at altitudes of 5700m and 5100m above sea level. (2) Methods: The present study investigated the polyphasic features and genomic characteristics of S5-59T and S8-45T. (3) Results: The major fatty acids and the predominant respiratory menaquinone of S5-59T and S8-45T were summed as feature 3 (comprising C16:1 ω6c and/or C16:1 ω7c) and ubiquinone-10 (Q-10). Phylogenetic analyses based on 16S rRNA sequences and average nucleotide identity values among these two strains and their reference type strains were below the species demarcation thresholds of 98.65% and 95%. Strains S5-59T and S8-45T harbored great radiation resistance. The genomic analyses showed that DNA damage repair genes, such as mutL, mutS, radA, radC, recF, recN, etc., were present in the S5-59T and S8-45T strains. Additionally, strain S5-59T possessed more genes related to DNA protection proteins. The pan-genome analysis and horizontal gene transfers revealed that strains of Sphingomonas had a consistently homologous genetic evolutionary radiation resistance. Moreover, enzymatic antioxidative proteins also served critical roles in converting ROS into harmless molecules that resulted in resistance to radiation. Further, pigments and carotenoids such as zeaxanthin and alkylresorcinols of the non-enzymatic antioxidative system were also predicted to protect them from radiation. (4) Conclusions: Type strains S5-59T (=JCM 35564T =GDMCC 1.3193T) and S8-45T (=JCM 34749T =GDMCC 1.2715T) represent two novel species of the genus Sphingomonas with the proposed name Sphingomonas qomolangmaensis sp. nov. and Sphingomonas glaciei sp. nov. The type strains, S5-59T and S8-45T, were assessed in a deeply genomic study of their radiation-resistant mechanisms and this thus resulted in a further understanding of their greater potential application for the development of anti-radiation protective drugs.
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Affiliation(s)
- Yang Liu
- State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
- University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing 100049, China
- Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Lanzhou 730000, China
| | - Xiaowen Cui
- Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Lanzhou 730000, China
- Key Laboratory of Desert and Desertification, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
- College of Geography and Environment Science, Northwest Normal University, Lanzhou 730070, China
| | - Ruiqi Yang
- College of Urban Environment, Lanzhou City University, Lanzhou 730070, China
| | - Yiyang Zhang
- Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Lanzhou 730000, China
- Key Laboratory of Desert and Desertification, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Yeteng Xu
- State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
- University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing 100049, China
- Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Lanzhou 730000, China
| | - Guangxiu Liu
- Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Lanzhou 730000, China
- Key Laboratory of Desert and Desertification, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
- School of Stomatology, Lanzhou University, Lanzhou 730000, China
| | - Binglin Zhang
- State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
- Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Lanzhou 730000, China
| | - Jinxiu Wang
- Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Lanzhou 730000, China
- Key Laboratory of Desert and Desertification, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Xinyue Wang
- University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing 100049, China
- Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Lanzhou 730000, China
- Key Laboratory of Desert and Desertification, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Wei Zhang
- Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Lanzhou 730000, China
- Key Laboratory of Desert and Desertification, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Tuo Chen
- State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
- Correspondence: (T.C.); (G.Z.)
| | - Gaosen Zhang
- Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Lanzhou 730000, China
- Key Laboratory of Desert and Desertification, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
- Correspondence: (T.C.); (G.Z.)
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7
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Sanderson H, Gray KL, Manuele A, Maguire F, Khan A, Liu C, Navanekere Rudrappa C, Nash JHE, Robertson J, Bessonov K, Oloni M, Alcock BP, Raphenya AR, McAllister TA, Peacock SJ, Raven KE, Gouliouris T, McArthur AG, Brinkman FSL, Fink RC, Zaheer R, Beiko RG. Exploring the mobilome and resistome of Enterococcus faecium in a One Health context across two continents. Microb Genom 2022; 8. [PMID: 36129737 DOI: 10.1099/mgen.0.000880] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Enterococcus faecium is a ubiquitous opportunistic pathogen that is exhibiting increasing levels of antimicrobial resistance (AMR). Many of the genes that confer resistance and pathogenic functions are localized on mobile genetic elements (MGEs), which facilitate their transfer between lineages. Here, features including resistance determinants, virulence factors and MGEs were profiled in a set of 1273 E. faecium genomes from two disparate geographic locations (in the UK and Canada) from a range of agricultural, clinical and associated habitats. Neither lineages of E. faecium, type A and B, nor MGEs are constrained by geographic proximity, but our results show evidence of a strong association of many profiled genes and MGEs with habitat. Many features were associated with a group of clinical and municipal wastewater genomes that are likely forming a new human-associated ecotype within type A. The evolutionary dynamics of E. faecium make it a highly versatile emerging pathogen, and its ability to acquire, transmit and lose features presents a high risk for the emergence of new pathogenic variants and novel resistance combinations. This study provides a workflow for MGE-centric surveillance of AMR in Enterococcus that can be adapted to other pathogens.
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Affiliation(s)
- Haley Sanderson
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, Canada
| | - Kristen L Gray
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Colombia, Canada
| | - Alexander Manuele
- Faculty of Computer Science, Dalhousie University, Halifax, Nova Scotia, Canada.,Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Finlay Maguire
- Faculty of Computer Science, Dalhousie University, Halifax, Nova Scotia, Canada.,Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Community Health & Epidemiology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Amjad Khan
- Faculty of Computer Science, Dalhousie University, Halifax, Nova Scotia, Canada.,Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Chaoyue Liu
- Faculty of Computer Science, Dalhousie University, Halifax, Nova Scotia, Canada.,Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Mathematics & Statistics, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Chandana Navanekere Rudrappa
- Faculty of Computer Science, Dalhousie University, Halifax, Nova Scotia, Canada.,Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia, Canada
| | - John H E Nash
- National Microbiology Laboratory, Public Health Agency of Canada, Guelph and Toronto, Ontario, Canada
| | - James Robertson
- National Microbiology Laboratory, Public Health Agency of Canada, Guelph and Toronto, Ontario, Canada
| | - Kyrylo Bessonov
- National Microbiology Laboratory, Public Health Agency of Canada, Guelph and Toronto, Ontario, Canada
| | - Martins Oloni
- Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.,David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Brian P Alcock
- Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.,David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Amogelang R Raphenya
- Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.,David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Tim A McAllister
- Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, Alberta, Canada
| | | | - Kathy E Raven
- Department of Medicine, Cambridge University, Cambridge, UK
| | | | - Andrew G McArthur
- Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.,David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Fiona S L Brinkman
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Colombia, Canada
| | - Ryan C Fink
- Faculty of Computer Science, Dalhousie University, Halifax, Nova Scotia, Canada.,Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Rahat Zaheer
- Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, Alberta, Canada
| | - Robert G Beiko
- Faculty of Computer Science, Dalhousie University, Halifax, Nova Scotia, Canada.,Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia, Canada
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8
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Yang R, Zhang B, Xu Y, Zhang G, Liu Y, Zhang D, Zhang W, Chen T, Liu G. Genomic insights revealed the environmental adaptability of Planococcus halotolerans Y50 isolated from petroleum-contaminated soil on the Qinghai-Tibet Plateau. Gene 2022; 823:146368. [PMID: 35240255 DOI: 10.1016/j.gene.2022.146368] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 02/17/2022] [Accepted: 02/18/2022] [Indexed: 11/28/2022]
Abstract
The Tibetan Plateau niche provides unprecedented opportunities to find microbes that are functional and commercial significance. The present study investigated the physiological and genomic characteristics of Planococcus halotolerans Y50 that was isolated from a petroleum-contaminated soil sample from the Qinghai-Tibet Plateau, and it displayed psychrotolerant, antiradiation, and oil-degraded characteristics. Whole genome sequencing indicated that strain Y50 has a 3.52 Mb genome and 44.7% G + C content, and it possesses 3377 CDSs. The presence of a wide range of UV damage repair genes uvrX and uvsE, DNA repair genes radA and recN, superoxide dismutase, peroxiredoxin and dioxygenase genes provided the genomic basis for the adaptation of the plateau environment polluted by petroleum. Related experiments also verified that the Y50 strain could degrade n-alkanes from C11-C23, and approximately 30% of the total petroleum at 25 °C within 7 days. Meanwhile, strain Y50 could withstand 5 × 103 J/m2 UVC and 10 KGy gamma ray radiation, and it had strong antioxidant and high radical scavengers for superoxide anion, hydroxyl radical and DPPH. In addition, pan-genome analysis and horizontal gene transfers revealed that strains with different niches have obtained various genes through horizontal gene transfer in the process of evolution, and the more similar their geographical locations, the more similar their members are genetically and ecologically. In conclusion, P. halotolerans Y50 possesses high potential of applications in the bioremediation of alpine hydrocarbons contaminated environment.
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Affiliation(s)
- Ruiqi Yang
- College of Urban Environment, Lanzhou City University, Lanzhou 730070, China; Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Gansu Province, 730000, China
| | - Binglin Zhang
- State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy Sciences, Lanzhou 730000, China; Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Gansu Province, 730000, China.
| | - Yeteng Xu
- State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy Sciences, Lanzhou 730000, China; Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Gansu Province, 730000, China
| | - Gaosen Zhang
- Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Gansu Province, 730000, China; Key Laboratory of Desert and Desertification, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Yang Liu
- Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Gansu Province, 730000, China; Key Laboratory of Desert and Desertification, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Dongming Zhang
- School of Engineering Sciences in Chemistry, Biotechnology, and Health (CBH), KTH Royal Institute of Technology, Stockholm, Sweden
| | - Wei Zhang
- Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Gansu Province, 730000, China; Key Laboratory of Desert and Desertification, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Tuo Chen
- State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy Sciences, Lanzhou 730000, China; Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Gansu Province, 730000, China
| | - Guangxiu Liu
- Key Laboratory of Extreme Environmental Microbial Resources and Engineering, Gansu Province, 730000, China; Key Laboratory of Desert and Desertification, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
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9
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Abstract
Horizontal gene transfer (HGT) is arguably the most conspicuous feature of bacterial evolution. Evidence for HGT is found in most bacterial genomes. Although HGT can considerably alter bacterial genomes, not all transfer events may be biologically significant and may instead represent the outcome of an incessant evolutionary process that only occasionally has a beneficial purpose. When adaptive transfers occur, HGT and positive selection may result in specific, detectable signatures in genomes, such as gene-specific sweeps or increased transfer rates for genes that are ecologically relevant. In this Review, we first discuss the various mechanisms whereby HGT occurs, how the genetic signatures shape patterns of genomic variation and the distinct bioinformatic algorithms developed to detect these patterns. We then discuss the evolutionary theory behind HGT and positive selection in bacteria, and discuss the approaches developed over the past decade to detect transferred DNA that may be involved in adaptation to new environments.
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10
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Koh XP, Shen Z, Woo CF, Yu Y, Lun HI, Cheung SW, Kwan JKC, Lau SCK. Genetic and Ecological Diversity of Escherichia coli and Cryptic Escherichia Clades in Subtropical Aquatic Environments. Front Microbiol 2022; 13:811755. [PMID: 35250929 PMCID: PMC8891540 DOI: 10.3389/fmicb.2022.811755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 01/12/2022] [Indexed: 11/13/2022] Open
Abstract
Escherichia coli not only inhabit the large intestines of human and warm-blooded animals but could also persist in the external environment. However, current knowledge was largely based on host-associated strains. Moreover, cryptic Escherichia clades that were often misidentified as E. coli by conventional diagnostic methods were discovered. Failure to distinguish them from E. coli sensu stricto could lead to inaccurate conclusions about the population genetics of E. coli. Based on seven housekeeping genes, we determine the genetic and ecological diversity of E. coli and cryptic clades as they occupy aquatic habitats with different characteristics and human impact levels in subtropical Hong Kong. Contrary to previous reports, clade II was the most abundant cryptic lineage co-isolated with E. coli, being especially abundant in relatively pristine subtropical aquatic environments. The phylogenetically distinct cryptic clades and E. coli showed limited recombination and significant genetic divergence. Analyses indicated that these clade II strains were ecologically differentiated from typical E. coli; some may even represent novel environmental Escherichia clades that were closely related to the original clade II strains of fecal origins. E. coli of diverse origins exhibited clonality amidst divergent genotypes STs, echoing other studies in that recombination in housekeeping genes was insufficient to disrupt phylogenetic signals of the largely clonal E. coli. Notably, environmental E. coli were less diverse than fecal isolates despite contributing many new alleles and STs. Finally, we demonstrated that human activities influenced the distribution of E. coli and clade II in a small aquatic continuum. Moving from relatively pristine sites toward areas with higher human disturbance, the abundance of clade II isolates and new E. coli genotypes reduces, while E. coli bearing class I integrons and belonging to CCs of public health concern accumulates. Altogether, this work revealed the new genetic diversity of E. coli and cryptic clades embedded in selected subtropical aquatic habitats, especially relatively pristine sites, which will aid a more thorough understanding of the extent of their genetic and functional variations in relation to diverse habitats with varied conditions.
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Affiliation(s)
- Xiu Pei Koh
- Division of Environment and Sustainability, The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China
| | - Zhiyong Shen
- Department of Ocean Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China
| | - Chun Fai Woo
- Division of Environment and Sustainability, The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China
| | - Yanping Yu
- Department of Ocean Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China
| | - Hau In Lun
- Department of Ocean Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China
| | - Sze Wan Cheung
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong, Hong Kong SAR, China
| | - Joseph Kai Cho Kwan
- Division of Environment and Sustainability, The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China
| | - Stanley Chun Kwan Lau
- Department of Ocean Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China
- *Correspondence: Stanley Chun Kwan Lau,
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11
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Igai K, Kitade O, Fu J, Omata K, Yonezawa T, Ohkuma M, Hongoh Y. Fine-scale genetic diversity and putative ecotypes of oxymonad protists coinhabiting the hindgut of Reticulitermes speratus. Mol Ecol 2021; 31:1317-1331. [PMID: 34865251 DOI: 10.1111/mec.16309] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 11/22/2021] [Accepted: 11/30/2021] [Indexed: 11/29/2022]
Abstract
The hindgut of lower termites is generally coinhabited by multiple morphologically identifiable protist species. However, it is unclear how many protist species truly coexist in this miniaturized environment, and moreover, it is difficult to define the fundamental unit of protist diversity. Species delineation of termite gut protists has therefore been guided without a theory-based concept of species. Here, we focused on the hindgut of the termite Reticulitermes speratus, where 10 or 11 morphologically distinct oxymonad cell types, that is, morphospecies, coexist. We elucidated the phylogenetic structure of all co-occurring oxymonads and addressed whether their diversity can be explained by the "ecotype" hypothesis. Oxymonad-specific 18S rRNA gene amplicon sequencing analyses of whole-gut samples, combined with single-cell 18S rRNA sequencing of the oxymonad morphospecies, identified 210 one-nucleotide-level variants. The phylogenetic analysis of these variants revealed the presence of microdiverse clusters typically within 1% sequence divergence. Each known oxymonad morphospecies comprised one to several monophyletic or paraphyletic microdiverse clusters. Using these sequence data sets, we conducted computational simulation to predict the rates of ecotype formation and periodic selection, and to demarcate putative ecotypes. Our simulations suggested that the oxymonad genetic divergence is constrained primarily by strong selection, in spite of limited population size and possible bottlenecks during intergenerational transmission. A total of 33 oxymonad ecotypes were predicted, and most of the putative ecotypes were consistently detected among different colonies and host individuals. These findings provide a possible theoretical basis for species diversity and underlying mechanisms of coexistence of termite gut protists.
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Affiliation(s)
- Katsura Igai
- School of Life Science and Technology, Tokyo Institute of Technology, Tokyo, Japan
| | - Osamu Kitade
- College of Science, Ibaraki University, Ibaraki, Japan
| | - Jieyang Fu
- School of Life Science and Technology, Tokyo Institute of Technology, Tokyo, Japan
| | - Kazumi Omata
- Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan.,Department of Hematology, Rheumatology and Infectious Disease, Kumamoto University Hospital, Kumamoto, Japan
| | - Takahiro Yonezawa
- Department of Animal Science, Faculty of Agriculture, Tokyo University of Agriculture, Kanagawa, Japan
| | - Moriya Ohkuma
- Microbe Division/Japan Collection of Microorganisms, RIKEN BioResource Research Center, Ibaraki, Japan
| | - Yuichi Hongoh
- School of Life Science and Technology, Tokyo Institute of Technology, Tokyo, Japan.,Microbe Division/Japan Collection of Microorganisms, RIKEN BioResource Research Center, Ibaraki, Japan
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12
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Genotyping and multivariate regression trees reveal ecological diversification within the Microcystis aeruginosa complex along a wide environmental gradient. Appl Environ Microbiol 2021; 88:e0147521. [PMID: 34818109 DOI: 10.1128/aem.01475-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Addressing the ecological and evolutionary processes underlying biodiversity patterns is essential to identify the mechanisms shaping community structure and function. In bacteria, the formation of new ecologically distinct populations (ecotypes) is proposed as one of the main drivers of diversification. New ecotypes arise when mutations in key functional genes or acquisition of new metabolic pathways by horizontal gene transfer allow the population to exploit new resources, permitting their coexistence with the parental population. We previously reported the presence of microcystin-producing organisms of the Microcystis aeruginosa complex (toxic MAC) through an 800 km environmental gradient ranging from freshwater to estuarine-marine waters in South America. We hypothesize that the success of toxic MAC in such a gradient is due to the existence of very closely related populations that are ecologically distinct (ecotypes), each specialized to a specific arrangement of environmental variables. Here, we analyzed toxic MAC genetic diversity through qPCR and high-resolution melting analysis (HRMA) of a functional gene (mcyJ, microcystin synthetase cluster). We explored the variability of the mcyJ gene along the environmental gradient by multivariate classification and regression trees (mCART). Six groups of mcyJ genotypes were distinguished and associated with different combinations of water temperature, conductivity and turbidity. We propose that each mcyJ variant associated to a defined environmental condition is an ecotype (or species) whose relative abundances vary according to their fitness in the local environment. This mechanism would explain the success of toxic MAC in such a wide array of environmental conditions. Importance Organisms of the Microcystis aeruginosa Complex form harmful algal blooms (HABs) in nutrient-rich water bodies worldwide. MAC HABs are difficult to manage owing to the production of potent toxins (microcystins) that resist water treatment. Besides, the role of microcystins in the ecology of MAC organisms is still elusive, meaning that the environmental conditions driving the toxicity of the bloom are not clear. Furthermore, the lack of coherence between morphology-based and genomic-based species classification makes it difficult to draw sound conclusions about when and where each member species of the MAC will dominate the bloom. Here, we propose that the diversification process and success of toxic MAC in a wide range of waterbodies involves the generation of ecotypes, each specialized in a particular niche, whose relative abundance varies according to its fitness in the local environment. This knowledge can improve the generation of accurate prediction models of MAC growth and toxicity, helping to prevent human and animal intoxication.
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13
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Pennycook JH, Scanlan PD. Ecological and Evolutionary responses to Antibiotic Treatment in the Human Gut Microbiota. FEMS Microbiol Rev 2021; 45:fuab018. [PMID: 33822937 PMCID: PMC8498795 DOI: 10.1093/femsre/fuab018] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 03/25/2021] [Indexed: 12/16/2022] Open
Abstract
The potential for antibiotics to affect the ecology and evolution of the human gut microbiota is well recognised and has wide-ranging implications for host health. Here, we review the findings of key studies that surveyed the human gut microbiota during antibiotic treatment. We find several broad patterns including the loss of diversity, disturbance of community composition, suppression of bacteria in the Actinobacteria phylum, amplification of bacteria in the Bacteroidetes phylum, and promotion of antibiotic resistance. Such changes to the microbiota were often, but not always, recovered following the end of treatment. However, many studies reported unique and/or contradictory results, which highlights our inability to meaningfully predict or explain the effects of antibiotic treatment on the human gut microbiome. This problem arises from variation between existing studies in three major categories: differences in dose, class and combinations of antibiotic treatments used; differences in demographics, lifestyles, and locations of subjects; and differences in measurements, analyses and reporting styles used by researchers. To overcome this, we suggest two integrated approaches: (i) a top-down approach focused on building predictive models through large sample sizes, deep metagenomic sequencing, and effective collaboration; and (ii) a bottom-up reductionist approach focused on testing hypotheses using model systems.
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Affiliation(s)
- Joseph Hugh Pennycook
- APC Microbiome Ireland, Biosciences Institute, University College Cork, College Road, Cork, T12 YT20, Ireland
- School of Mirobiology, Food Science & Technology Building, University College Cork, College Road, Cork, T12 K8AF, Ireland
| | - Pauline Deirdre Scanlan
- APC Microbiome Ireland, Biosciences Institute, University College Cork, College Road, Cork, T12 YT20, Ireland
- School of Mirobiology, Food Science & Technology Building, University College Cork, College Road, Cork, T12 K8AF, Ireland
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14
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Novick A, Doolittle WF. 'Species' without species. STUDIES IN HISTORY AND PHILOSOPHY OF SCIENCE 2021; 87:72-80. [PMID: 34111824 DOI: 10.1016/j.shpsa.2021.03.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 12/23/2020] [Accepted: 03/18/2021] [Indexed: 06/12/2023]
Abstract
Biological science uses multiple species concepts. Order can be brought to this diversity if we recognize two key features. First, any given species concept is likely to have a patchwork structure, generated by repeated application of the concept to new domains. We illustrate this by showing how two species concepts (biological and ecological) have been modified from their initial eukaryotic applications to apply to prokaryotes. Second, both within and between patches, distinct species concepts may interact and hybridize. We thus defend a semantic picture of the species concept as a collection of interacting patchwork structures. Thus, although not all uses of the term pick out the same kind of unit in nature, the diversity of uses reflects something more than mere polysemy. We suggest that the emphasis on the use of species to pick out natural units is itself problematic, because that is not the term's sole function. In particular, species concepts are used to manage inquiry into processes of speciation, even when these processes do not produce clearly delimited species.
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Affiliation(s)
- Aaron Novick
- Department of Philosophy, University of Washington, Seattle, WA, USA.
| | - W Ford Doolittle
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, Canada
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15
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Harrow GL, Lees JA, Hanage WP, Lipsitch M, Corander J, Colijn C, Croucher NJ. Negative frequency-dependent selection and asymmetrical transformation stabilise multi-strain bacterial population structures. THE ISME JOURNAL 2021; 15:1523-1538. [PMID: 33408365 PMCID: PMC8115253 DOI: 10.1038/s41396-020-00867-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 12/01/2020] [Accepted: 12/03/2020] [Indexed: 02/06/2023]
Abstract
Streptococcus pneumoniae can be divided into many strains, each a distinct set of isolates sharing similar core and accessory genomes, which co-circulate within the same hosts. Previous analyses suggested the short-term vaccine-associated dynamics of S. pneumoniae strains may be mediated through multi-locus negative frequency-dependent selection (NFDS), which maintains accessory loci at equilibrium frequencies. Long-term simulations demonstrated NFDS stabilised clonally-evolving multi-strain populations through preventing the loss of variation through drift, based on polymorphism frequencies, pairwise genetic distances and phylogenies. However, allowing symmetrical recombination between isolates evolving under multi-locus NFDS generated unstructured populations of diverse genotypes. Replication of the observed data improved when multi-locus NFDS was combined with recombination that was instead asymmetrical, favouring deletion of accessory loci over insertion. This combination separated populations into strains through outbreeding depression, resulting from recombinants with reduced accessory genomes having lower fitness than their parental genotypes. Although simplistic modelling of recombination likely limited these simulations' ability to maintain some properties of genomic data as accurately as those lacking recombination, the combination of asymmetrical recombination and multi-locus NFDS could restore multi-strain population structures from randomised initial populations. As many bacteria inhibit insertions into their chromosomes, this combination may commonly underlie the co-existence of strains within a niche.
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Affiliation(s)
- Gabrielle L Harrow
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, Norfolk Place, London, W2 1PG, UK
| | - John A Lees
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, Norfolk Place, London, W2 1PG, UK
| | - William P Hanage
- Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Avenue, Boston, MA, 02115, USA
| | - Marc Lipsitch
- Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Avenue, Boston, MA, 02115, USA
| | - Jukka Corander
- Department of Biostatistics, University of Oslo, Oslo, Norway
- Helsinki Institute of Information Technology, Department of Mathematics and Statistics, University of Helsinki, Helsinki, Finland
- Parasites & Microbes Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, UK
| | - Caroline Colijn
- Parasites & Microbes Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, UK
- Department of Mathematics, Simon Fraser University, Burnaby, BC, Canada
| | - Nicholas J Croucher
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, Norfolk Place, London, W2 1PG, UK.
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16
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Guerrero LD, Pérez MV, Orellana E, Piuri M, Quiroga C, Erijman L. Long-run bacteria-phage coexistence dynamics under natural habitat conditions in an environmental biotechnology system. THE ISME JOURNAL 2021; 15:636-648. [PMID: 33067586 PMCID: PMC8027832 DOI: 10.1038/s41396-020-00802-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 09/21/2020] [Accepted: 10/01/2020] [Indexed: 01/30/2023]
Abstract
Bacterial viruses are widespread and abundant across natural and engineered habitats. They influence ecosystem functioning through interactions with their hosts. Laboratory studies of phage-host pairs have advanced our understanding of phenotypic and genetic diversification in bacteria and phages. However, the dynamics of phage-host interactions have been seldom recorded in complex natural environments. We conducted an observational metagenomic study of the dynamics of interaction between Gordonia and their phages using a three-year data series of samples collected from a full-scale wastewater treatment plant. The aim was to obtain a comprehensive picture of the coevolution dynamics in naturally evolving populations at relatively high time resolution. Coevolution was followed by monitoring changes over time in the CRISPR loci of Gordonia metagenome-assembled genome, and reciprocal changes in the viral genome. Genome-wide analysis indicated low strain variability of Gordonia, and almost clonal conservation of the trailer end of the CRISPR loci. Incorporation of newer spacers gave rise to multiple coexisting bacterial populations. The host population carrying a shorter CRISPR locus that contain only ancestral spacers, which has not acquired newer spacers against the coexisting phages, accounted for more than half of the total host abundance in the majority of samples. Phages genome co-evolved by introducing directional changes, with no preference for mutations within the protospacer and PAM regions. Metagenomic reconstruction of time-resolved variants of host and viral genomes revealed how the complexity at the population level has important consequences for bacteria-phage coexistence.
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Affiliation(s)
- Leandro D. Guerrero
- grid.423606.50000 0001 1945 2152Instituto de Investigaciones en Ingeniería Genética y Biología Molecular “Dr Héctor N. Torres” (INGEBI-CONICET), Vuelta de Obligado 2490, C1428ADN Buenos Aires, Argentina
| | - María V. Pérez
- grid.423606.50000 0001 1945 2152Instituto de Investigaciones en Ingeniería Genética y Biología Molecular “Dr Héctor N. Torres” (INGEBI-CONICET), Vuelta de Obligado 2490, C1428ADN Buenos Aires, Argentina ,Agua y Saneamientos Argentinos S.A., Tucumán 752, C1049APP Buenos Aires, Argentina
| | - Esteban Orellana
- grid.423606.50000 0001 1945 2152Instituto de Investigaciones en Ingeniería Genética y Biología Molecular “Dr Héctor N. Torres” (INGEBI-CONICET), Vuelta de Obligado 2490, C1428ADN Buenos Aires, Argentina
| | - Mariana Piuri
- Departamento de Química Biológica, Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, CONICET, Intendente Güiraldes 2160, C1428EGA Buenos Aires, Argentina
| | - Cecilia Quiroga
- Instituto de Investigaciones en Microbiología y Parasitología Médica (IMPaM), Facultad de Medicina, Universidad de Buenos Aires, CONICET, Paraguay 2155, C1121ABG Buenos Aires, Argentina
| | - Leonardo Erijman
- grid.423606.50000 0001 1945 2152Instituto de Investigaciones en Ingeniería Genética y Biología Molecular “Dr Héctor N. Torres” (INGEBI-CONICET), Vuelta de Obligado 2490, C1428ADN Buenos Aires, Argentina ,grid.7345.50000 0001 0056 1981Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires, Intendente Güiraldes 2160s, C1428EGA Buenos Aires, Argentina
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17
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Kang Y, Yuan L, Shi X, Chu Y, He Z, Jia X, Lin Q, Ma Q, Wang J, Xiao J, Hu S, Gao Z, Chen F, Yu J. A fine-scale map of genome-wide recombination in divergent Escherichia coli population. Brief Bioinform 2020; 22:6034796. [PMID: 33319232 DOI: 10.1093/bib/bbaa335] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 10/19/2020] [Accepted: 10/23/2020] [Indexed: 01/09/2023] Open
Abstract
Recombination is one of the most important molecular mechanisms of prokaryotic genome evolution, but its exact roles are still in debate. Here we try to infer genome-wide recombination within a species, utilizing a dataset of 149 complete genomes of Escherichia coli from diverse animal hosts and geographic origins, including 45 in-house sequenced with the single-molecular real-time platform. Two major clades identified based on physiological, clinical and ecological characteristics form distinct genetic lineages based on scarcity of interclade gene exchanges. By defining gene-based syntenies for genomic segments within and between the two clades, we build a fine-scale recombination map for this representative global E. coli population. The map suggests extensive within-clade recombination that often breaks physical linkages among individual genes but seldom interrupts the structure of genome organizational frameworks as well as primary metabolic portfolios supported by the framework integrity, possibly due to strong natural selection for both physiological compatibility and ecological fitness. In contrast, the between-clade recombination declines drastically when phylogenetic distance increases to the extent where a 10-fold reduction can be observed, establishing a firm genetic barrier between clades. Our empirical data suggest a critical role for such recombination events in the early stage of speciation where recombination rate is associated with phylogenetic distance in addition to sequence and gene variations. The extensive intraclade recombination binds sister strains into a quasisexual group and optimizes genes or alleles to streamline physiological activities, whereas the sharply declined interclade recombination split the population into clades adaptive to divergent ecological niches.
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Affiliation(s)
- Yu Kang
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, 100101, Beijing, PR China.,China National Center for Bioinformation, Beijing 100101, PR China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lina Yuan
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, 100101, Beijing, PR China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xing Shi
- Department of Respiratory & Critical Care Medicine, Peking University People's Hospital, Beijing, 100044, PR China
| | - Yanan Chu
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, 100101, Beijing, PR China.,China National Center for Bioinformation, Beijing 100101, PR China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zilong He
- Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, Interdisciplinary Innovation Institute of Medicine and Engineering, Beihang University, Beijing, 100191, PR China
| | - Xinmiao Jia
- Medical Research Center, Peking Union Medical College Hospital, Peking Union Medical College & Chinese Academy of Medical Sciences, Beijing 100730, PR China
| | - Qiang Lin
- Shenzhen Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, China
| | - Qin Ma
- Department of Agronomy, Horticulture, and Plant Science, South Dakota State University, Brookings, SD, 57007, USA
| | - Jian Wang
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, 100101, Beijing, PR China.,China National Center for Bioinformation, Beijing 100101, PR China
| | - Jingfa Xiao
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, 100101, Beijing, PR China.,China National Center for Bioinformation, Beijing 100101, PR China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Songnian Hu
- University of Chinese Academy of Sciences, Beijing 100049, China.,State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, 100101, Beijing, PR China
| | - Zhancheng Gao
- Department of Respiratory & Critical Care Medicine, Peking University People's Hospital, Beijing, 100044, PR China
| | - Fei Chen
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, 100101, Beijing, PR China.,China National Center for Bioinformation, Beijing 100101, PR China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jun Yu
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, 100101, Beijing, PR China.,China National Center for Bioinformation, Beijing 100101, PR China.,University of Chinese Academy of Sciences, Beijing 100049, China
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18
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Genetic Variation and Preliminary Indications of Divergent Niche Adaptation in Cryptic Clade II of Escherichia. Microorganisms 2020; 8:microorganisms8111713. [PMID: 33142902 PMCID: PMC7716201 DOI: 10.3390/microorganisms8111713] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 10/24/2020] [Accepted: 10/30/2020] [Indexed: 12/03/2022] Open
Abstract
The evolution, habitat, and lifestyle of the cryptic clade II of Escherichia, which were first recovered at low frequency from non-human hosts and later from external environments, were poorly understood. Here, the genomes of selected strains were analyzed for preliminary indications of ecological differentiation within their population. We adopted the delta bitscore metrics to detect functional divergence of their orthologous genes and trained a random forest classifier to differentiate the genomes according to habitats (gastrointestinal vs external environment). Model was built with inclusion of other Escherichia genomes previously demonstrated to have exhibited genomic traits of adaptation to one of the habitats. Overall, gene degradation was more prominent in the gastrointestinal strains. The trained model correctly classified the genomes, identifying a set of predictor genes that were informative of habitat association. Functional divergence in many of these genes were reflective of ecological divergence. Accuracy of the trained model was confirmed by its correct prediction of the habitats of an independent set of strains with known habitat association. In summary, the cryptic clade II of Escherichia displayed genomic signatures that are consistent with divergent adaptation to gastrointestinal and external environments.
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19
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The evolution of bacterial pathogens in the Anthropocene. INFECTION GENETICS AND EVOLUTION 2020; 86:104611. [PMID: 33130070 DOI: 10.1016/j.meegid.2020.104611] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 10/23/2020] [Accepted: 10/27/2020] [Indexed: 12/18/2022]
Abstract
Humankind has become a primary driver of global environmental and climate change. The extent of planetary change is such that it has been proposed to classify the current geological age as the 'Anthropocene'. Anthropogenic environmental degradation presents numerous threats to human health and wellbeing, including an increased risk of infectious disease. This review focuses on how processes such as pollution, climate change and human-mediated dispersal could affect the evolution of bacterial pathogens. Effects of environmental change on the 'big five' of evolution: mutation rate, recombination (horizontal gene transfer), migration, selection and drift are discussed. Microplastic pollution is used as a case study to highlight the combined effects of some of these processes on the evolutionary diversification of human pathogens. Although the evidence is still incomplete, a picture is emerging that environmental pathogens could evolve at increased rates in the Anthropocene, with potential consequences for human infection.
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20
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Towards Genomic Criteria for Delineating Fungal Species. J Fungi (Basel) 2020; 6:jof6040246. [PMID: 33114441 PMCID: PMC7711752 DOI: 10.3390/jof6040246] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 10/15/2020] [Accepted: 10/23/2020] [Indexed: 02/06/2023] Open
Abstract
The discussion of fungal species delineation has yet to reach a consensus, despite the advancements in technology, which helped modernise traditional approaches. In particular, the phylogenetic species concept was one of the tools that has been used with considerable success across the fungal kingdom. The fast rise of fungal genomics provides an unprecedented opportunity to expand measuring the relatedness of fungal strains to the level of whole genomes. However, the use of genomic information in taxonomy has only just begun, and few methodological guidelines have been suggested so far. Here, a simple approach of computationally measuring genomic distances and their use as a standard for species delineation is investigated. A fixed threshold genomic distance calculated by the quick and easy-to-use tools Mash and Dashing proved to be an unexpectedly widely applicable and robust criterion for determining whether two genomes belong to the same or to different species. The accuracy of species delineation in an uncurated dataset of GenBank fungal genomes was close to 90%—and exceeded 90% with minimal curation. As expected, the discriminative power of this approach was lower at higher taxonomic ranks, but still significantly larger than zero. Simple instructions for calculation of a genomic distance between two genomes and species similarity thresholds at different k-mer sizes are suggested. The calculation of genomic distance is identified as a powerful approach for delineating fungal species and is proposed—not as the only criterion—but as an additional tool in the versatile toolbox of fungal taxonomy.
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21
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Abstract
As the most abundant bacteria in oceans, the Pelagibacterales order (here SAR11) plays an important role in the global carbon cycle, but the study of the evolutionary forces driving its evolution has lagged considerably due to the inherent difficulty of obtaining pure cultures. Multiple evolutionary models have been proposed to explain the diversification of distinct lineages within a population; however, the identification of many of these patterns in natural populations remains mostly enigmatic. We have used a metagenomic approach to explore microdiversity patterns in their natural habitats. Comparison with a collection of bacterial and archaeal groups from the same environments shows that SAR11 populations have a different evolutionary regime, where multiple genotypes coexist within the same population and remain stable over time. Widespread homologous recombination could be one of the main driving factors of this homogenization. The SAR11 clade of Alphaproteobacteria is the most abundant group of planktonic cells in the near-surface epipelagic waters of the ocean, but the mechanisms underlying its exceptional success have not been fully elucidated. Here, we applied a metagenomic approach to explore microdiversity patterns by measuring the accumulation of synonymous and nonsynonymous mutations as well as homologous recombination in populations of SAR11 from different aquatic habitats (marine epipelagic, bathypelagic, and surface freshwater). The patterns of mutation accumulation and recombination were compared to those of other groups of representative marine microbes with multiple ecological strategies that share the same marine habitat, namely, Cyanobacteria (Prochlorococcus and Synechococcus), Archaea (“Candidatus Nitrosopelagicus” and Marine Group II Thalassoarchaea), and some heterotrophic marine bacteria (Alteromonas and Erythrobacter). SAR11 populations showed widespread recombination among distantly related members, preventing divergence leading to a genetically stable population. Moreover, their high intrapopulation sequence diversity with an enrichment in synonymous replacements supports the idea of a very ancient divergence and the coexistence of multiple different clones. However, other microbes analyzed seem to follow different evolutionary dynamics where processes of diversification driven by geographic and ecological instability produce a higher number of nonsynonymous replacements and lower intrapopulation sequence diversity. Together, these data shed light on some of the evolutionary and ecological processes that lead to the large genomic diversity in SAR11. Furthermore, this approach can be applied to other similar microbes that are difficult to culture in the laboratory, but abundant in nature, to investigate the underlying dynamics of their genomic evolution. IMPORTANCE As the most abundant bacteria in oceans, the Pelagibacterales order (here SAR11) plays an important role in the global carbon cycle, but the study of the evolutionary forces driving its evolution has lagged considerably due to the inherent difficulty of obtaining pure cultures. Multiple evolutionary models have been proposed to explain the diversification of distinct lineages within a population; however, the identification of many of these patterns in natural populations remains mostly enigmatic. We have used a metagenomic approach to explore microdiversity patterns in their natural habitats. Comparison with a collection of bacterial and archaeal groups from the same environments shows that SAR11 populations have a different evolutionary regime, where multiple genotypes coexist within the same population and remain stable over time. Widespread homologous recombination could be one of the main driving factors of this homogenization.
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22
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Stabilization of extensive fine-scale diversity by ecologically driven spatiotemporal chaos. Proc Natl Acad Sci U S A 2020; 117:14572-14583. [PMID: 32518107 DOI: 10.1073/pnas.1915313117] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
It has recently become apparent that the diversity of microbial life extends far below the species level to the finest scales of genetic differences. Remarkably, extensive fine-scale diversity can coexist spatially. How is this diversity stable on long timescales, despite selective or ecological differences and other evolutionary processes? Most work has focused on stable coexistence or assumed ecological neutrality. We present an alternative: extensive diversity maintained by ecologically driven spatiotemporal chaos, with no assumptions about niches or other specialist differences between strains. We study generalized Lotka-Volterra models with antisymmetric correlations in the interactions inspired by multiple pathogen strains infecting multiple host strains. Generally, these exhibit chaos with increasingly wild population fluctuations driving extinctions. But the simplest spatial structure, many identical islands with migration between them, stabilizes a diverse chaotic state. Some strains (subspecies) go globally extinct, but many persist for times exponentially long in the number of islands. All persistent strains have episodic local blooms to high abundance, crucial for their persistence as, for many, their average population growth rate is negative. Snapshots of the abundance distribution show a power law at intermediate abundances that is essentially indistinguishable from the neutral theory of ecology. But the dynamics of the large populations are much faster than birth-death fluctuations. We argue that this spatiotemporally chaotic "phase" should exist in a wide range of models, and that even in rapidly mixed systems, longer-lived spores could similarly stabilize a diverse chaotic phase.
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23
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Drewnowska JM, Stefanska N, Czerniecka M, Zambrowski G, Swiecicka I. Potential Enterotoxicity of Phylogenetically Diverse Bacillus cereus Sensu Lato Soil Isolates from Different Geographical Locations. Appl Environ Microbiol 2020; 86:e03032-19. [PMID: 32220844 PMCID: PMC7237779 DOI: 10.1128/aem.03032-19] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Accepted: 03/20/2020] [Indexed: 02/06/2023] Open
Abstract
Bacillus cereus sensu lato comprises Gram-positive spore-forming bacteria producing toxins associated with foodborne diseases. Three pore-forming enterotoxins, nonhemolytic enterotoxin (Nhe), hemolysin BL (Hbl), and cytotoxin K (CytK), are considered the primary factors in B. cereus sensu lato diarrhea. The aim of this study was to determine the potential risk of enterotoxicity among soil B. cereus sensu lato isolates representing diverse phylogroups and originated from different geographic locations with various climates (Burkina Faso, Kenya, Argentina, Kazakhstan, and Poland). While nheA- and hblA-positive isolates were present among all B. cereus sensu lato populations and distributed across all phylogenetic groups, cytK-2-positive strains predominated in geographic regions with an arid hot climate (Africa) and clustered together on a phylogenetic tree mainly within mesophilic groups III and IV. The highest in vitro cytotoxicity to Caco-2 and HeLa cells was demonstrated by the strains clustered within phylogroups II and IV. Overall, our results suggest that B. cereus sensu lato pathogenicity is a comprehensive process conditioned by many intracellular factors and diverse environmental conditions.IMPORTANCE This research offers a new route for a wider understanding of the dependency between pathogenicity and phylogeny of a natural bacterial population, specifically within Bacillus cereus sensu lato, that is widely distributed around the world and easily transferred into food products. Our study indicates differences in the phylogenetic and geographical distributions of potential enterotoxigenic B. cereus sensu lato strains. Hence, these bacilli possess a risk for human health, and rapid testing methods for their identification are greatly needed. In particular, the detection of the CytK enterotoxin should be a supporting strategy for the identification of pathogenic B. cereus sensu lato.
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Affiliation(s)
| | - Natalia Stefanska
- Department of Microbiology, Faculty of Biology, University of Bialystok, Bialystok, Poland
| | - Magdalena Czerniecka
- Department of Cytobiochemistry, Faculty of Biology, University of Bialystok, Bialystok, Poland
- Laboratory of Tissue Culture, Faculty of Biology, University of Bialystok, Bialystok, Poland
| | - Grzegorz Zambrowski
- Laboratory of Applied Microbiology, University of Bialystok, Bialystok, Poland
| | - Izabela Swiecicka
- Department of Microbiology, Faculty of Biology, University of Bialystok, Bialystok, Poland
- Laboratory of Applied Microbiology, University of Bialystok, Bialystok, Poland
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24
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Moulana A, Anderson RE, Fortunato CS, Huber JA. Selection Is a Significant Driver of Gene Gain and Loss in the Pangenome of the Bacterial Genus Sulfurovum in Geographically Distinct Deep-Sea Hydrothermal Vents. mSystems 2020; 5:e00673-19. [PMID: 32291353 PMCID: PMC7159903 DOI: 10.1128/msystems.00673-19] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 03/30/2020] [Indexed: 12/20/2022] Open
Abstract
Microbial genomes have highly variable gene content, and the evolutionary history of microbial populations is shaped by gene gain and loss mediated by horizontal gene transfer and selection. To evaluate the influence of selection on gene content variation in hydrothermal vent microbial populations, we examined 22 metagenome-assembled genomes (MAGs) (70 to 97% complete) from the ubiquitous vent Epsilonbacteraeota genus Sulfurovum that were recovered from two deep-sea hydrothermal vent regions, Axial Seamount in the northeastern Pacific Ocean (13 MAGs) and the Mid-Cayman Rise in the Caribbean Sea (9 MAGs). Genes involved in housekeeping functions were highly conserved across Sulfurovum lineages. However, genes involved in environment-specific functions, and in particular phosphate regulation, were found mostly in Sulfurovum genomes from the Mid-Cayman Rise in the low-phosphate Atlantic Ocean environment, suggesting that nutrient limitation is an important selective pressure for these bacteria. Furthermore, genes that were rare within the pangenome were more likely to undergo positive selection than genes that were highly conserved in the pangenome, and they also appeared to have experienced gene-specific sweeps. Our results suggest that selection is a significant driver of gene gain and loss for dominant microbial lineages in hydrothermal vents and highlight the importance of factors like nutrient limitation in driving microbial adaptation and evolution.IMPORTANCE Microbes can alter their gene content through the gain and loss of genes. However, there is some debate as to whether natural selection or neutral processes play a stronger role in molding the gene content of microbial genomes. In this study, we examined variation in gene content for the Epsilonbacteraeota genus Sulfurovum from deep-sea hydrothermal vents, which are dynamic habitats known for extensive horizontal gene transfer within microbial populations. Our results show that natural selection is a strong driver of Sulfurovum gene content and that nutrient limitation in particular has shaped the Sulfurovum genome, leading to differences in gene content between ocean basins. Our results also suggest that recently acquired genes undergo stronger selection than genes that were acquired in the more distant past. Overall, our results highlight the importance of natural selection in driving the evolution of microbial populations in these dynamic habitats.
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Affiliation(s)
- Alief Moulana
- Biology Department, Carleton College, Northfield, Minnesota, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
| | - Rika E Anderson
- Biology Department, Carleton College, Northfield, Minnesota, USA
| | | | - Julie A Huber
- Marine Chemistry & Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
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25
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Becraft ED, Wood JM, Cohan FM, Ward DM. Biogeography of American Northwest Hot Spring A/B '-Lineage Synechococcus Populations. Front Microbiol 2020; 11:77. [PMID: 32153516 PMCID: PMC7050468 DOI: 10.3389/fmicb.2020.00077] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 01/15/2020] [Indexed: 12/17/2022] Open
Abstract
Previous analyses have shown how diversity among unicellular cyanobacteria inhabiting island-like hot springs is structured relative to physical separation and physiochemical differences among springs, especially at local to regional scales. However, these studies have been limited by the low resolution provided by the molecular markers surveyed. We analyzed large datasets obtained by high-throughput sequencing of a segment of the photosynthesis gene psaA from samples collected in hot springs from geothermal basins in Yellowstone National Park, Montana, and Oregon, all known from previous studies to contain populations of A/B'-lineage Synechococcus. The fraction of identical sequences was greater among springs separated by <50 km than among springs separated by >50 km, and springs separated by >800 km shared sequence variants only rarely. Phylogenetic analyses provided evidence for endemic lineages that could be related to geographic isolation and/or geochemical differences on regional scales. Ecotype Simulation 2 was used to predict putative ecotypes (ecologically distinct populations), and their membership, and canonical correspondence analysis was used to examine the geographical and geochemical bases for variation in their distribution. Across the range of Oregon and Yellowstone, geographical separation explained the largest percentage of the differences in distribution of ecotypes (9.5% correlated to longitude; 9.4% to latitude), with geochemical differences explaining the largest percentage of the remaining differences in distribution (7.4-9.3% correlated to magnesium, sulfate, and sulfide). Among samples within the Greater Yellowstone Ecosystem, geochemical differences significantly explained the distribution of ecotypes (6.5-9.3% correlated to magnesium, boron, sulfate, silicon dioxide, chloride, and pH). Nevertheless, differences in the abundance and membership of ecotypes in Yellowstone springs with similar chemistry suggested that allopatry may be involved even at local scales. Synechococcus populations have diverged both by physical isolation and physiochemical differences, and populations on surprisingly local scales have been evolving independently.
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Affiliation(s)
- Eric D Becraft
- Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, United States.,Department of Biology, University of North Alabama, Florence, AL, United States
| | - Jason M Wood
- Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, United States.,Biotechnology and Planetary Protection Group, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States
| | - Frederick M Cohan
- Department of Biology, Wesleyan University, Middletown, CT, United States
| | - David M Ward
- Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, United States
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26
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Baker BJ, Crane-Kramer G, Dee MW, Gregoricka LA, Henneberg M, Lee C, Lukehart SA, Mabey DC, Roberts CA, Stodder ALW, Stone AC, Winingear S. Advancing the understanding of treponemal disease in the past and present. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2020; 171 Suppl 70:5-41. [PMID: 31956996 DOI: 10.1002/ajpa.23988] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Revised: 12/04/2019] [Accepted: 12/05/2019] [Indexed: 12/11/2022]
Abstract
Syphilis was perceived to be a new disease in Europe in the late 15th century, igniting a debate about its origin that continues today in anthropological, historical, and medical circles. We move beyond this age-old debate using an interdisciplinary approach that tackles broader questions to advance the understanding of treponemal infection (syphilis, yaws, bejel, and pinta). How did the causative organism(s) and humans co-evolve? How did the related diseases caused by Treponema pallidum emerge in different parts of the world and affect people across both time and space? How are T. pallidum subspecies related to the treponeme causing pinta? The current state of scholarship in specific areas is reviewed with recommendations made to stimulate future work. Understanding treponemal biology, genetic relationships, epidemiology, and clinical manifestations is crucial for vaccine development today and for investigating the distribution of infection in both modern and past populations. Paleopathologists must improve diagnostic criteria and use a standard approach for recording skeletal lesions on archaeological human remains. Adequate contextualization of cultural and environmental conditions is necessary, including site dating and justification for any corrections made for marine or freshwater reservoir effects. Biogeochemical analyses may assess aquatic contributions to diet, physiological changes arising from treponemal disease and its treatments (e.g., mercury), or residential mobility of those affected. Shifting the focus from point of origin to investigating who is affected (e.g., by age/sex or socioeconomic status) and disease distribution (e.g., coastal/ inland, rural/urban) will advance our understanding of the treponemal disease and its impact on people through time.
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Affiliation(s)
- Brenda J Baker
- School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona
| | - Gillian Crane-Kramer
- Department of Anthropology, State University of New York at Plattsburgh, Plattsburgh, New York
| | - Michael W Dee
- Centre for Isotope Research, University of Groningen, Groningen, Netherlands
| | - Lesley A Gregoricka
- Department of Sociology, Anthropology, and Social Work, University of South Alabama, Mobile, Alabama
| | - Maciej Henneberg
- Biological Anthropology and Comparative Anatomy Unit, Adelaide Medical School, University of Adelaide, Adelaide, Australia.,Institute of Evolutionary Medicine, University of Zurich, Zurich, Switzerland
| | - Christine Lee
- Department of Anthropology, California State University Los Angeles, Los Angeles, California
| | - Sheila A Lukehart
- Department of Medicine/Infectious Diseases and Global Health, University of Washington, Seattle, Washington
| | - David C Mabey
- Communicable Diseases, London School of Hygiene & Tropical Medicine, London, UK
| | | | - Ann L W Stodder
- Office of Archaeological Studies, The Museum of New Mexico, Santa Fe, New Mexico
| | - Anne C Stone
- School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona
| | - Stevie Winingear
- School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona
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27
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Comparative Genomics Analysis of Lactobacillus ruminis from Different Niches. Genes (Basel) 2020; 11:genes11010070. [PMID: 31936280 PMCID: PMC7016997 DOI: 10.3390/genes11010070] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 01/04/2020] [Accepted: 01/06/2020] [Indexed: 01/14/2023] Open
Abstract
Lactobacillus ruminis is a commensal motile lactic acid bacterium living in the intestinal tract of humans and animals. Although a few genomes of L. ruminis were published, most of them were animal derived. To explore the genetic diversity and potential niche-specific adaptation changes of L. ruminis, in the current work, draft genomes of 81 L. ruminis strains isolated from human, bovine, piglet, and other animals were sequenced, and comparative genomic analysis was performed. The genome size and GC content of L. ruminis on average were 2.16 Mb and 43.65%, respectively. Both the origin and the sampling distance of these strains had a great influence on the phylogenetic relationship. For carbohydrate utilization, the human-derived L. ruminis strains had a higher consistency in the utilization of carbon source compared to the animal-derived strains. L. ruminis mainly increased the competitiveness of niches by producing class II bacteriocins. The type of clustered regularly interspaced short palindromic repeats /CRISPR-associated (CRISPR/Cas) system presented in L. ruminis was mainly subtype IIA. The diversity of CRISPR/Cas locus depended on the high denaturation of spacer number and sequence, although cas1 protein was relatively conservative. The genetic differences in those newly sequenced L. ruminis strains highlighted the gene gains and losses attributed to niche adaptations.
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28
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Liu L, Zhu K, Wurzburger N, Zhang J. Relationships between plant diversity and soil microbial diversity vary across taxonomic groups and spatial scales. Ecosphere 2020. [DOI: 10.1002/ecs2.2999] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Affiliation(s)
- Lan Liu
- Zhejiang Tiantong Forest Ecosystem National Observation and Research Station & Shanghai Key Lab for Urban Ecological Processes and Eco‐Restoration School of Ecological and Environmental Sciences East China Normal University Shanghai 200241 China
- Department of Environmental Studies University of California Santa Cruz California 95064 USA
- Shanghai Institute of Pollution Control and Ecological Security Shanghai 200092 China
| | - Kai Zhu
- Department of Environmental Studies University of California Santa Cruz California 95064 USA
| | - Nina Wurzburger
- Odum School of Ecology University of Georgia Athens Georgia 30602 USA
| | - Jian Zhang
- Zhejiang Tiantong Forest Ecosystem National Observation and Research Station & Shanghai Key Lab for Urban Ecological Processes and Eco‐Restoration School of Ecological and Environmental Sciences East China Normal University Shanghai 200241 China
- Shanghai Institute of Pollution Control and Ecological Security Shanghai 200092 China
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29
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Delmont TO, Kiefl E, Kilinc O, Esen OC, Uysal I, Rappé MS, Giovannoni S, Eren AM. Single-amino acid variants reveal evolutionary processes that shape the biogeography of a global SAR11 subclade. eLife 2019; 8:46497. [PMID: 31478833 PMCID: PMC6721796 DOI: 10.7554/elife.46497] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Accepted: 08/13/2019] [Indexed: 12/14/2022] Open
Abstract
Members of the SAR11 order Pelagibacterales dominate the surface oceans. Their extensive diversity challenges emerging operational boundaries defined for microbial 'species' and complicates efforts of population genetics to study their evolution. Here, we employed single-amino acid variants (SAAVs) to investigate ecological and evolutionary forces that maintain the genomic heterogeneity within ubiquitous SAR11 populations we accessed through metagenomic read recruitment using a single isolate genome. Integrating amino acid and protein biochemistry with metagenomics revealed that systematic purifying selection against deleterious variants governs non-synonymous variation among very closely related populations of SAR11. SAAVs partitioned metagenomes into two main groups matching large-scale oceanic current temperatures, and six finer proteotypes that connect distant oceanic regions. These findings suggest that environmentally-mediated selection plays a critical role in the journey of cosmopolitan surface ocean microbial populations, and the idea 'everything is everywhere but the environment selects' has credence even at the finest resolutions.
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Affiliation(s)
- Tom O Delmont
- Department of Medicine, The University of Chicago, Chicago, United States
| | - Evan Kiefl
- Department of Medicine, The University of Chicago, Chicago, United States.,Graduate Program in Biophysical Sciences, University of Chicago, Chicago, United States
| | - Ozsel Kilinc
- Department of Electrical Engineering, University of South Florida, Tampa, United States
| | - Ozcan C Esen
- Department of Medicine, The University of Chicago, Chicago, United States
| | - Ismail Uysal
- Department of Electrical Engineering, University of South Florida, Tampa, United States
| | - Michael S Rappé
- Hawaii Institute of Marine Biology, University of Hawaii at Manoa, Kaneohe, United States
| | - Steven Giovannoni
- Department of Microbiology, Oregon State University, Corvallis, United States
| | - A Murat Eren
- Department of Medicine, The University of Chicago, Chicago, United States.,Marine Biological Laboratory, Woods Hole, United States
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30
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Kumar N, Browne HP, Viciani E, Forster SC, Clare S, Harcourt K, Stares MD, Dougan G, Fairley DJ, Roberts P, Pirmohamed M, Clokie MRJ, Jensen MBF, Hargreaves KR, Ip M, Wieler LH, Seyboldt C, Norén T, Riley TV, Kuijper EJ, Wren BW, Lawley TD. Adaptation of host transmission cycle during Clostridium difficile speciation. Nat Genet 2019; 51:1315-1320. [PMID: 31406348 DOI: 10.1038/s41588-019-0478-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 06/04/2019] [Indexed: 12/20/2022]
Abstract
Bacterial speciation is a fundamental evolutionary process characterized by diverging genotypic and phenotypic properties. However, the selective forces that affect genetic adaptations and how they relate to the biological changes that underpin the formation of a new bacterial species remain poorly understood. Here, we show that the spore-forming, healthcare-associated enteropathogen Clostridium difficile is actively undergoing speciation. Through large-scale genomic analysis of 906 strains, we demonstrate that the ongoing speciation process is linked to positive selection on core genes in the newly forming species that are involved in sporulation and the metabolism of simple dietary sugars. Functional validation shows that the new C. difficile produces spores that are more resistant and have increased sporulation and host colonization capacity when glucose or fructose is available for metabolism. Thus, we report the formation of an emerging C. difficile species, selected for metabolizing simple dietary sugars and producing high levels of resistant spores, that is adapted for healthcare-mediated transmission.
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Affiliation(s)
- Nitin Kumar
- Host-Microbiota Interactions Laboratory, Wellcome Sanger Institute, Hinxton, UK.
| | - Hilary P Browne
- Host-Microbiota Interactions Laboratory, Wellcome Sanger Institute, Hinxton, UK
| | - Elisa Viciani
- Host-Microbiota Interactions Laboratory, Wellcome Sanger Institute, Hinxton, UK
| | - Samuel C Forster
- Host-Microbiota Interactions Laboratory, Wellcome Sanger Institute, Hinxton, UK.,Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, Victoria, Australia.,Department of Molecular and Translational Sciences, Monash University, Clayton, Victoria, Australia
| | | | | | - Mark D Stares
- Host-Microbiota Interactions Laboratory, Wellcome Sanger Institute, Hinxton, UK
| | | | - Derek J Fairley
- Belfast Health and Social Care Trust, Belfast, Northern, Ireland
| | | | | | - Martha R J Clokie
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, UK
| | | | - Katherine R Hargreaves
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, UK
| | - Margaret Ip
- Department of Microbiology, Chinese University of Hong Kong, Shatin, Hong Kong
| | - Lothar H Wieler
- Institute of Microbiology and Epizootics, Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany.,Robert Koch Institute, Berlin, Germany
| | - Christian Seyboldt
- Institute of Bacterial Infections and Zoonoses, Federal Research Institute for Animal Health (Friedrich-Loeffler-Institut), Jena, Germany
| | - Torbjörn Norén
- Faculty of Medicine and Health, Örebro University, Örebro, Sweden.,Department of Laboratory Medicine, Örebro University Hospital Örebro, Örebro, Sweden
| | - Thomas V Riley
- Department of Microbiology, PathWest Laboratory Medicine, Queen Elizabeth II Medical Centre, Nedlands, Western Australia, Australia.,School of Pathology & Laboratory Medicine, The University of Western Australia, Nedlands, Western Australia, Australia
| | - Ed J Kuijper
- Section Experimental Bacteriology, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - Brendan W Wren
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, University of London, London, UK
| | - Trevor D Lawley
- Host-Microbiota Interactions Laboratory, Wellcome Sanger Institute, Hinxton, UK.
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31
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Miller SR, Carvey D. Ecological Divergence with Gene Flow in a Thermophilic Cyanobacterium. MICROBIAL ECOLOGY 2019; 78:33-41. [PMID: 30267129 DOI: 10.1007/s00248-018-1267-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 09/19/2018] [Indexed: 06/08/2023]
Abstract
How ecological diversity is maintained and distributed within populations is a longstanding question in microbial ecology. In the thermophilic cyanobacterium Synechococcus B', high observed levels of recombination are predicted to maintain ecological variation despite the simultaneous action of diverse selective pressures on different regions of the genome. To investigate ecological diversity in these bacteria, we directly isolated laboratory strains of Synechococcus B' from samples collected along the thermal gradients of two geothermal environments in Yellowstone National Park. Extensive recombination was evident for a multi-locus sequence data set, and, consequently, our sample did not exhibit the sequence clustering expected for distinct ecotypes evolving by periodic clonal selection. Evidence for local selective sweeps at specific loci suggests that sweeps may be common but that recombination is effective for maintaining diversity of unlinked genomic regions. Thermal performance for strain growth was positively associated with the temperature of the environment, indicating that Synechococcus B' populations consist of locally adapted ecological specialists that occupy specific thermal niches. Because this ecological differentiation is observed despite the absence of dispersal barriers among sites, we conclude that these bacteria may freely exchange much of the genome but that barriers to gene flow exist for loci under direct temperature selection.
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Affiliation(s)
- Scott R Miller
- Division of Biological Sciences, The University of Montana, 32 Campus Dr. #4824, Missoula, MT, 59812, USA.
| | - Darla Carvey
- Division of Biological Sciences, The University of Montana, 32 Campus Dr. #4824, Missoula, MT, 59812, USA
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32
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Díez-Vives C, Nielsen S, Sánchez P, Palenzuela O, Ferrera I, Sebastián M, Pedrós-Alió C, Gasol JM, Acinas SG. Delineation of ecologically distinct units of marine Bacteroidetes in the Northwestern Mediterranean Sea. Mol Ecol 2019; 28:2846-2859. [PMID: 30830717 DOI: 10.1111/mec.15068] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 02/13/2019] [Accepted: 02/27/2019] [Indexed: 01/18/2023]
Abstract
Bacteroidetes is one of the dominant phyla of ocean bacterioplankton, yet its diversity and population structure is poorly understood. To advance in the delineation of ecologically meaningful units within this group, we constructed near full-length 16S rRNA gene clone libraries from contrasting marine environments in the NW Mediterranean. Based on phylogeny and the associated ecological variables (depth and season), 24 different Bacteroidetes clades were delineated. By considering their relative abundance (from iTag amplicon sequencing studies), we described the distribution patterns of each of these clades, delimiting them as Ecologically Significant Taxonomic Units (ESTUs). Spatially, there was almost no overlap among ESTUs at different depths. In deep waters there was predominance of Owenweeksia, Leeuwenhoekiella, Muricauda-related genera, and some depth-associated ESTUs within the NS5 and NS2b marine clades. Seasonally, multi-annual dynamics of recurring ESTUs were present with dominance of some ESTUs within the NS4, NS5 and NS2b marine clades along most of the year, but with variable relative frequencies between months. A drastic change towards the predominance of Formosa-related ESTUs and one ESTU from the NS5 marine clade was typically present after the spring bloom. Even though there are no isolates available for these ESTUs to determine their physiology, correlation analyses identified the environmental preference of some of them. Overall, our results suggest that there is a high degree of niche specialisation within these closely related clades. This work constitutes a step forward in disentangling the ecology of marine Bacteroidetes, which are essential players in organic matter processing in the oceans.
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Affiliation(s)
- Cristina Díez-Vives
- Department of Marine Biology and Oceanography, Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain.,Department of Life Sciences (Invertebrate Division), The Natural History Museum of London, London, UK
| | - Shaun Nielsen
- School of Biotechnology and Biomolecular Sciences, Centre for Marine Bio-Innovation, The University of New South Wales, Sydney, New South Wales, Australia
| | - Pablo Sánchez
- Department of Marine Biology and Oceanography, Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain
| | - Oswaldo Palenzuela
- Department of Biology, Culture and Pathology of Marine Species, Instituto de Acuicultura Torre de la Sal, Ribera de Cabanes, Spain
| | - Isabel Ferrera
- Department of Marine Biology and Oceanography, Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain.,Instituto Español de Oceanografía, Centro Oceanográfico de Málaga, Fuengirola, Spain
| | - Marta Sebastián
- Department of Marine Biology and Oceanography, Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain.,Instituto de Oceanografía y Cambio Global, IOCAG, Universidad de las Palmas de Gran Canaria, ULPGC, Telde, Spain
| | - Carlos Pedrós-Alió
- Department of Marine Biology and Oceanography, Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain.,Departamento de Biología de Sistemas, Centro Nacional de Biotecnología, Madrid, Spain
| | - Josep M Gasol
- Department of Marine Biology and Oceanography, Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain.,Centre for Marine Ecosystems Research, School of Science, Edith Cowan University, Joondalup, Western Australia, Australia
| | - Silvia G Acinas
- Department of Marine Biology and Oceanography, Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain
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Affiliation(s)
- Aaron Novick
- Department of Philosophy, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
- * E-mail: (AN); (WFD)
| | - W. Ford Doolittle
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
- * E-mail: (AN); (WFD)
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Schmutzer M, Barraclough TG. The role of recombination, niche-specific gene pools and flexible genomes in the ecological speciation of bacteria. Ecol Evol 2019; 9:4544-4556. [PMID: 31031926 PMCID: PMC6476844 DOI: 10.1002/ece3.5052] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 02/16/2019] [Accepted: 02/18/2019] [Indexed: 12/21/2022] Open
Abstract
Bacteria diversify into genetic clusters analogous to those observed in sexual eukaryotes, but the definition of bacterial species is an ongoing problem. Recent work has focused on adaptation to distinct ecological niches as the main driver of clustering, but there remains debate about the role of recombination in that process. One view is that homologous recombination occurs too rarely for gene flow to constrain divergent selection. Another view is that homologous recombination is frequent enough in many bacterial populations that barriers to gene flow are needed to permit divergence. Niche-specific gene pools have been proposed as a general mechanism to limit gene flow. We use theoretical models to evaluate additional hypotheses that evolving genetic architecture, specifically the effect sizes of genes and gene gain and loss, can limit gene flow between diverging populations. Our model predicts that (a) in the presence of gene flow and recombination, ecological divergence is concentrated in few loci of large effect and (b) high rates of gene flow plus recombination promote gene loss and favor the evolution of niche-specific genes. The results show that changing genetic architecture and gene loss can facilitate ecological divergence, even without niche-specific gene pools. We discuss these results in the context of recent studies of sympatric divergence in microbes.
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Population Genomics Insights into Adaptive Evolution and Ecological Differentiation in Streptomycetes. Appl Environ Microbiol 2019; 85:AEM.02555-18. [PMID: 30658977 DOI: 10.1128/aem.02555-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 01/14/2019] [Indexed: 12/20/2022] Open
Abstract
Deciphering the genomic variation that represents microevolutionary processes toward species divergence is key to understanding microbial speciation, which has long been under debate. Streptomycetes are filamentous bacteria that are ubiquitous in nature and the richest source of antibiotics; however, their speciation processes remain unknown. To tackle this issue, we performed a comprehensive population genomics analysis on Streptomyces albidoflavus residing in different habitats and with a worldwide distribution and identified and characterized the foundational changes within the species. We detected three well-defined phylogenomic clades, of which clades I and III mainly contained free-living (soil/marine) and insect-associated strains, respectively, and clade II had a mixed origin. By performing genome-wide association studies (GWAS), we identified a number of genetic variants associated with free-living or entomic (denoting or relating to insects) habitats in both the accessory and core genomes. These variants contributed collectively to the population structure and had annotated or confirmed functions that likely facilitate differential adaptation of the species. In addition, we detected higher levels of homologous recombination within each clade and in the free-living group than within the whole species and in the entomic group. A subset of the insect-associated strains (clade III) showed a relatively independent evolutionary trajectory with more symbiosis-favorable genes but little genetic interchange with the other lineages. Our results demonstrate that ecological adaptation promotes genetic differentiation in S. albidoflavus, suggesting a model of ecological speciation with gene flow in streptomycetes.IMPORTANCE Species are the fundamental units of ecology and evolution, and speciation leads to the astounding diversity of life on Earth. Studying speciation is thus of great significance to understand, protect, and exploit biodiversity, but it is a challenge in the microbial world. In this study, using population genomics, we placed Streptomyces albidoflavus strains in a spectrum of speciation and showed that the genetic differences between phylogenomic clusters evolved mainly by environmental selection and gene-specific sweeps. These findings highlight the role of ecology in structuring recombining bacterial species, making a step toward a deeper understanding of microbial speciation. Our results also raise concerns of an underrated microbial diversity at the intraspecies level, which can be utilized for mining of ecologically relevant natural products.
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36
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Palmer M, Venter SN, Coetzee MP, Steenkamp ET. Prokaryotic species are sui generis evolutionary units. Syst Appl Microbiol 2019; 42:145-158. [DOI: 10.1016/j.syapm.2018.10.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 10/02/2018] [Accepted: 10/03/2018] [Indexed: 12/25/2022]
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37
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Hanson CA, Müller AL, Loy A, Dona C, Appel R, Jørgensen BB, Hubert CRJ. Historical Factors Associated With Past Environments Influence the Biogeography of Thermophilic Endospores in Arctic Marine Sediments. Front Microbiol 2019; 10:245. [PMID: 30873129 PMCID: PMC6403435 DOI: 10.3389/fmicb.2019.00245] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 01/29/2019] [Indexed: 11/13/2022] Open
Abstract
Selection by the local, contemporary environment plays a prominent role in shaping the biogeography of microbes. However, the importance of historical factors in microbial biogeography is more debatable. Historical factors include past ecological and evolutionary circumstances that may have influenced present-day microbial diversity, such as dispersal and past environmental conditions. Diverse thermophilic sulfate-reducing Desulfotomaculum are present as dormant endospores in marine sediments worldwide where temperatures are too low to support their growth. Therefore, they are dispersed to here from elsewhere, presumably a hot, anoxic habitat. While dispersal through ocean currents must influence their distribution in cold marine sediments, it is not clear whether even earlier historical factors, related to the source habitat where these organisms were once active, also have an effect. We investigated whether these historical factors may have influenced the diversity and distribution of thermophilic endospores by comparing their diversity in 10 Arctic fjord surface sediments. Although community composition varied spatially, clear biogeographic patterns were only evident at a high level of taxonomic resolution (>97% sequence similarity of the 16S rRNA gene) achieved with oligotyping. In particular, the diversity and distribution of oligotypes differed for the two most prominent OTUs (defined using a standard 97% similarity cutoff). One OTU was dominated by a single ubiquitous oligotype, while the other OTU consisted of ten more spatially localized oligotypes that decreased in compositional similarity with geographic distance. These patterns are consistent with differences in historical factors that occurred when and where the taxa were once active, prior to sporulation. Further, the influence of history on biogeographic patterns was only revealed by analyzing microdiversity within OTUs, suggesting that populations within standard OTU-level groupings do not necessarily share a common ecological and evolutionary history.
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Affiliation(s)
- China A Hanson
- School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Albert L Müller
- Division of Microbial Ecology, Department of Microbiology and Ecosystem Science, University of Vienna, Vienna, Austria
| | - Alexander Loy
- Division of Microbial Ecology, Department of Microbiology and Ecosystem Science, University of Vienna, Vienna, Austria.,Austrian Polar Research Institute, Vienna, Austria
| | - Clelia Dona
- School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Ramona Appel
- Department of Microbiology, Max Planck Institute for Marine Microbiology, Bremen, Germany
| | | | - Casey R J Hubert
- School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, United Kingdom.,Geomicrobiology Group, Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
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38
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Järvenpää M, Gutmann MU, Vehtari A, Marttinen P. Gaussian process modelling in approximate Bayesian computation to estimate horizontal gene transfer in bacteria. Ann Appl Stat 2018. [DOI: 10.1214/18-aoas1150] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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39
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Rosen MJ, Davison M, Fisher DS, Bhaya D. Probing the ecological and evolutionary history of a thermophilic cyanobacterial population via statistical properties of its microdiversity. PLoS One 2018; 13:e0205396. [PMID: 30427861 PMCID: PMC6235289 DOI: 10.1371/journal.pone.0205396] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 09/25/2018] [Indexed: 12/11/2022] Open
Abstract
Despite extensive DNA sequencing data derived from natural microbial communities, it remains a major challenge to identify the key evolutionary and ecological forces that shape microbial populations. We have focused on the extensive microdiversity of the cyanobacterium Synechococcus sp., which is a dominant member of the dense phototrophic biofilms in the hot springs of Yellowstone National Park. From deep amplicon sequencing of many loci and statistical analyses of these data, we showed previously that the population has undergone an unexpectedly high degree of homologous recombination, unlinking synonymous SNP-pair correlations even on intragenic length scales. Here, we analyze the genic amino acid diversity, which provides new evidence of selection and insights into the evolutionary history of the population. Surprisingly, some features of the data, including the spectrum of distances between genic-alleles, appear consistent with primarily asexual neutral drift. Yet the non-synonymous site frequency spectrum has too large an excess of low-frequency polymorphisms to result from negative selection on deleterious mutations given the distribution of coalescent times that we infer. And our previous analyses showed that the population is not asexual. Taken together, these apparently contradictory data suggest that selection, epistasis, and hitchhiking all play essential roles in generating and stabilizing the diversity. We discuss these as well as potential roles of ecological niches at genomic and genic levels. From quantitative properties of the diversity and comparative genomic data, we infer aspects of the history and inter-spring dispersal of the meta-population since it was established in the Yellowstone Caldera. Our investigations illustrate the need for combining multiple types of sequencing data and quantitative statistical analyses to develop an understanding of microdiversity in natural microbial populations.
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Affiliation(s)
- Michael J. Rosen
- Applied Physics Department, Stanford University, Stanford, CA, United States of America
| | - Michelle Davison
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, United States of America
| | - Daniel S. Fisher
- Applied Physics Department, Stanford University, Stanford, CA, United States of America
| | - Devaki Bhaya
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, United States of America
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40
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Temperature modulates Fischerella thermalis ecotypes in Porcelana Hot Spring. Syst Appl Microbiol 2018; 41:531-543. [PMID: 30041921 DOI: 10.1016/j.syapm.2018.05.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 05/18/2018] [Accepted: 05/23/2018] [Indexed: 11/21/2022]
Abstract
In the Porcelana Hot Spring (Northern Patagonia), true-branching cyanobacteria are the dominant primary producers in microbial mats, and they are mainly responsible for carbon and nitrogen fixation. However, little is known about their metabolic and genomic adaptations at high temperatures. Therefore, in this study, a total of 81 Fischerella thermalis strains (also known as Mastigocladus laminosus) were isolated from mat samples in a thermal gradient between 61-46°C. The complementary use of proteomic comparisons from these strains, and comparative genomics of F. thermalis pangenomes, suggested that at least two different ecotypes were present within these populations. MALDI-TOF MS analysis separated the strains into three clusters; two with strains obtained from mats within the upper temperature range (61 and 54°C), and a third obtained from mats within the lower temperature range (51 and 46°C). Both groups possessed different but synonymous nifH alleles. The main proteomic differences were associated with the abundance of photosynthesis-related proteins. Three F. thermalis metagenome assembled genomes (MAGs) were described from 66, 58 and 48°C metagenomes. These pangenomes indicated a divergence of orthologous genes and a high abundance of exclusive genes at 66°C. These results improved the current understanding of thermal adaptation of F. thermalis and the evolution of these thermophilic cyanobacterial species.
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Abstract
Any two lineages, no matter how distant they are now, began their divergence as one population splitting into two lineages that could coexist indefinitely. The rate of origin of higher-level taxa is therefore the product of the rate of speciation times the probability that two new species coexist long enough to reach a particular level of divergence. Here I have explored these two parameters of disparification in bacteria. Owing to low recombination rates, sexual isolation is not a necessary milestone of bacterial speciation. Rather, irreversible and indefinite divergence begins with ecological diversification, that is, transmission of a bacterial lineage to a new ecological niche, possibly to a new microhabitat but at least to new resources. Several algorithms use sequence data from a taxon of focus to identify phylogenetic groups likely to bear the dynamic properties of species. Identifying these newly divergent lineages allows us to characterize the genetic bases of speciation, as well as the ecological dimensions upon which new species diverge. Speciation appears to be least frequent when a given lineage has few new resources it can adopt, as exemplified by photoautotrophs, C1 heterotrophs, and obligately intracellular pathogens; speciation is likely most rapid for generalist heterotrophs. The genetic basis of ecological divergence may determine whether ecological divergence is irreversible and whether lineages will diverge indefinitely into the future. Long-term coexistence is most likely when newly divergent lineages utilize at least some resources not shared with the other and when the resources themselves will coexist into the remote future.
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42
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Freese HM, Sikorski J, Bunk B, Scheuner C, Meier-Kolthoff JP, Spröer C, Gram L, Overmann J. Trajectories and Drivers of Genome Evolution in Surface-Associated Marine Phaeobacter. Genome Biol Evol 2018; 9:3297-3311. [PMID: 29194520 PMCID: PMC5730936 DOI: 10.1093/gbe/evx249] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/27/2017] [Indexed: 12/19/2022] Open
Abstract
The extent of genome divergence and the evolutionary events leading to speciation of marine bacteria have mostly been studied for (locally) abundant, free-living groups. The genus Phaeobacter is found on different marine surfaces, seems to occupy geographically disjunct habitats, and is involved in different biotic interactions, and was therefore targeted in the present study. The analysis of the chromosomes of 32 closely related but geographically spread Phaeobacter strains revealed an exceptionally large, highly syntenic core genome. The flexible gene pool is constantly but slightly expanding across all Phaeobacter lineages. The horizontally transferred genes mostly originated from bacteria of the Roseobacter group and horizontal transfer most likely was mediated by gene transfer agents. No evidence for geographic isolation and habitat specificity of the different phylogenomic Phaeobacter clades was detected based on the sources of isolation. In contrast, the functional gene repertoire and physiological traits of different phylogenomic Phaeobacter clades were sufficiently distinct to suggest an adaptation to an associated lifestyle with algae, to additional nutrient sources, or toxic heavy metals. Our study reveals that the evolutionary trajectories of surface-associated marine bacteria can differ significantly from free-living marine bacteria or marine generalists.
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Affiliation(s)
- Heike M Freese
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany
| | - Johannes Sikorski
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany
| | - Boyke Bunk
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany
| | - Carmen Scheuner
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany
| | - Jan P Meier-Kolthoff
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany
| | - Cathrin Spröer
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany
| | - Lone Gram
- Department of Biotechnology and Bioengineering, Technical University of Denmark, Lyngby, Denmark
| | - Jörg Overmann
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany.,Institute of Microbiology, University Braunschweig, Germany
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43
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Inglin RC, Meile L, Stevens MJA. Clustering of Pan- and Core-genome of Lactobacillus provides Novel Evolutionary Insights for Differentiation. BMC Genomics 2018; 19:284. [PMID: 29690879 PMCID: PMC5937832 DOI: 10.1186/s12864-018-4601-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 03/13/2018] [Indexed: 01/21/2023] Open
Abstract
Background Bacterial taxonomy aims to classify bacteria based on true evolutionary events and relies on a polyphasic approach that includes phenotypic, genotypic and chemotaxonomic analyses. Until now, complete genomes are largely ignored in taxonomy. The genus Lactobacillus consists of 173 species and many genomes are available to study taxonomy and evolutionary events. Results We analyzed and clustered 98 completely sequenced genomes of the genus Lactobacillus and 234 draft genomes of 5 different Lactobacillus species, i.e. L. reuteri, L. delbrueckii, L. plantarum, L. rhamnosus and L. helveticus. The core-genome of the genus Lactobacillus contains 266 genes and the pan-genome 20′800 genes. Clustering of the Lactobacillus pan- and core-genome resulted in two highly similar trees. This shows that evolutionary history is traceable in the core-genome and that clustering of the core-genome is sufficient to explore relationships. Clustering of core- and pan-genomes at species’ level resulted in similar trees as well. Detailed analyses of the core-genomes showed that the functional class “genetic information processing” is conserved in the core-genome but that “signaling and cellular processes” is not. The latter class encodes functions that are involved in environmental interactions. Evolution of lactobacilli seems therefore directed by the environment. The type species L. delbrueckii was analyzed in detail and its pan-genome based tree contained two major clades whose members contained different genes yet identical functions. In addition, evidence for horizontal gene transfer between strains of L. delbrueckii, L. plantarum, and L. rhamnosus, and between species of the genus Lactobacillus is presented. Our data provide evidence for evolution of some lactobacilli according to a parapatric-like model for species differentiation. Conclusions Core-genome trees are useful to detect evolutionary relationships in lactobacilli and might be useful in taxonomic analyses. Lactobacillus’ evolution is directed by the environment and HGT. Electronic supplementary material The online version of this article (10.1186/s12864-018-4601-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Raffael C Inglin
- Laboratory of Food Biotechnology, Institute of Food, Nutrition and Health, ETH Zurich, Schmelzbergstrasse 7, 8092, Zurich, Switzerland
| | - Leo Meile
- Laboratory of Food Biotechnology, Institute of Food, Nutrition and Health, ETH Zurich, Schmelzbergstrasse 7, 8092, Zurich, Switzerland.
| | - Marc J A Stevens
- Laboratory of Food Biotechnology, Institute of Food, Nutrition and Health, ETH Zurich, Schmelzbergstrasse 7, 8092, Zurich, Switzerland.,Present address: Institute for Food Hygiene and Safety, University of Zurich, Winterthurerstrasse 272, 8057, Zurich, Switzerland
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44
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Rocha EPC. Neutral Theory, Microbial Practice: Challenges in Bacterial Population Genetics. Mol Biol Evol 2018; 35:1338-1347. [DOI: 10.1093/molbev/msy078] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Affiliation(s)
- Eduardo P C Rocha
- Microbial Evolutionary Genomics, Institut Pasteur, Paris, France
- CNRS, UMR3525, Paris, France
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45
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Roth‐Schulze AJ, Pintado J, Zozaya‐Valdés E, Cremades J, Ruiz P, Kjelleberg S, Thomas T. Functional biogeography and host specificity of bacterial communities associated with the Marine Green Alga
Ulva
spp. Mol Ecol 2018; 27:1952-1965. [DOI: 10.1111/mec.14529] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 01/30/2018] [Indexed: 01/21/2023]
Affiliation(s)
- Alexandra J. Roth‐Schulze
- Centre for Marine Bio‐Innovation School of Biological, Earth and Environmental Sciences The University of New South Wales Sydney NSW Australia
| | - José Pintado
- Centre for Marine Bio‐Innovation School of Biological, Earth and Environmental Sciences The University of New South Wales Sydney NSW Australia
- Instituto de Investigacións Mariñas (IIM ‐ CSIC) Vigo Spain
| | - Enrique Zozaya‐Valdés
- Centre for Marine Bio‐Innovation School of Biological, Earth and Environmental Sciences The University of New South Wales Sydney NSW Australia
| | - Javier Cremades
- BIOCOST Centro de Investigaciones Científicas Avanzadas (CICA) Universidade da Coruña A Coruña Spain
| | - Patricia Ruiz
- Instituto de Investigacións Mariñas (IIM ‐ CSIC) Vigo Spain
| | - Staffan Kjelleberg
- Centre for Marine Bio‐Innovation School of Biological, Earth and Environmental Sciences The University of New South Wales Sydney NSW Australia
| | - Torsten Thomas
- Centre for Marine Bio‐Innovation School of Biological, Earth and Environmental Sciences The University of New South Wales Sydney NSW Australia
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46
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Braga LPP, Soucy SM, Amgarten DE, da Silva AM, Setubal JC. Bacterial Diversification in the Light of the Interactions with Phages: The Genetic Symbionts and Their Role in Ecological Speciation. Front Ecol Evol 2018. [DOI: 10.3389/fevo.2018.00006] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
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47
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Riojas MA, McGough KJ, Rider-Riojas CJ, Rastogi N, Hazbón MH. Phylogenomic analysis of the species of the Mycobacterium tuberculosis complex demonstrates that Mycobacterium africanum, Mycobacterium bovis, Mycobacterium caprae, Mycobacterium microti and Mycobacterium pinnipedii are later heterotypic synonyms of Mycobacterium tuberculosis. Int J Syst Evol Microbiol 2017; 68:324-332. [PMID: 29205127 DOI: 10.1099/ijsem.0.002507] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The species within the Mycobacterium tuberculosis Complex (MTBC) have undergone numerous taxonomic and nomenclatural changes, leaving the true structure of the MTBC in doubt. We used next-generation sequencing (NGS), digital DNA-DNA hybridization (dDDH), and average nucleotide identity (ANI) to investigate the relationship between these species. The type strains of Mycobacterium africanum, Mycobacterium bovis, Mycobacterium caprae, Mycobacterium microti and Mycobacterium pinnipedii were sequenced via NGS. Pairwise dDDH and ANI comparisons between these, previously sequenced MTBC type strain genomes (including 'Mycobacterium canettii', 'Mycobacterium mungi' and 'Mycobacterium orygis') and M. tuberculosis H37RvT were performed. Further, all available genome sequences in GenBank for species in or putatively in the MTBC were compared to H37RvT. Pairwise results indicated that all of the type strains of the species are extremely closely related to each other (dDDH: 91.2-99.2 %, ANI: 99.21-99.92 %), greatly exceeding the respective species delineation thresholds, thus indicating that they belong to the same species. Results from the GenBank genomes indicate that all the strains examined are within the circumscription of H37RvT (dDDH: 83.5-100 %). We, therefore, formally propose a union of the species of the MTBC as M. tuberculosis. M. africanum, M. bovis, M. caprae, M. microti and M. pinnipedii are reclassified as later heterotypic synonyms of M. tuberculosis. 'M. canettii', 'M. mungi', and 'M. orygis' are classified as strains of the species M. tuberculosis. We further recommend use of the infrasubspecific term 'variant' ('var.') and infrasubspecific designations that generally retain the historical nomenclature associated with the groups or otherwise convey such characteristics, e.g. M. tuberculosis var. bovis.
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Affiliation(s)
| | - Katya J McGough
- ATCC®, Manassas, VA 20110, USA
- George Mason University, Fairfax, VA 22030, USA
| | | | - Nalin Rastogi
- Institut Pasteur de la Guadeloupe, Les Abymes 97139, Guadeloupe, France
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48
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Hoetzinger M, Hahn MW. Genomic divergence and cohesion in a species of pelagic freshwater bacteria. BMC Genomics 2017; 18:794. [PMID: 29037158 PMCID: PMC5644125 DOI: 10.1186/s12864-017-4199-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Accepted: 10/08/2017] [Indexed: 11/15/2022] Open
Abstract
Background In many prokaryotic genera a clustered phylogeny is observed, akin to the occurrence of species in sexually reproducing organisms. For some taxa, homologous recombination has been invoked as the underlying mechanism providing genomic cohesion among conspecific individuals. Whether this mechanism is applicable to prokaryotes in freshwaters with low habitat connectivity – i.e. elevated geographic barriers to gene flow – is unclear. To investigate further we studied genomic trends within the globally abundant PnecC cluster (genus Polynucleobacter, Betaproteobacteria) and analyzed homologous recombination within the affiliated species P. asymbioticus. Results Comparisons among 20 PnecC genomes revealed a clearly discontinuous distribution of nucleotide sequence similarities. Among the nine conspecific individuals (P. asymbioticus) all average nucleotide identity (ANI) values were greater than 97%, whereas all other comparisons exhibited ANI values lower than 85%. The reconstruction of recombination and mutation events for the P. asymbioticus core genomes yielded an r/m ratio of 7.4, which is clearly above estimated thresholds for recombination to act as a cohesive force. Hotspots of recombination were found to be located in the flanking regions of genomic islands. Even between geographically separated habitats a high flux of recombination was evident. While a biogeographic population structure was suggested from MLST data targeting rather conserved loci, such a structure was barely visible when whole genome data was considered. However, both MLST and whole genome data showed evidence of differentiation between two lineages of P. asymbioticus. The ratios of non-synonymous to synonymous substitution rates as well as growth rates in transplantation experiments suggested that this divergence was not selectively neutral. Conclusions The high extent of homologous recombination among P. asymbioticus bacteria can act as a cohesive force that effectively counteracts genetic divergence. At least on a regional scale, homologous recombination can act across geographically separated ecosystems and therefore plays an important role in the evolution and consistency of bacterial freshwater species. A species model akin to the biological species concept may be applicable for P. asymbioticus. Nonetheless, two genetically distinct lineages have emerged and further research may clarify if their divergence has been initiated by reinforced geographical barriers or has been evolving in sympatry. Electronic supplementary material The online version of this article (10.1186/s12864-017-4199-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Matthias Hoetzinger
- Research Institute for Limnology, University of Innsbruck, Mondseestrasse 9, A-5310, Mondsee, Austria.
| | - Martin W Hahn
- Research Institute for Limnology, University of Innsbruck, Mondseestrasse 9, A-5310, Mondsee, Austria
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Abstract
Ecosystems are commonly conceptualized as networks of interacting species. However, partitioning natural diversity of organisms into discrete units is notoriously problematic and mounting experimental evidence raises the intriguing question whether this perspective is appropriate for the microbial world. Here an alternative formalism is proposed that does not require postulating the existence of species as fundamental ecological variables and provides a naturally hierarchical description of community dynamics. This formalism allows approaching the species problem from the opposite direction. While the classical models treat a world of imperfectly clustered organism types as a perturbation around well-clustered species, the presented approach allows gradually adding structure to a fully disordered background. The relevance of this theoretical construct for describing highly diverse natural ecosystems is discussed.
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Affiliation(s)
- Mikhail Tikhonov
- Center of Mathematical Sciences and Applications, John A. Paulson School of Engineering and Applied Sciences, Kavli Institute for Bionano Science and Technology, Harvard University, 29 Oxford Street, Cambridge, Massachusetts 02138, USA and Department of Applied Physics, Stanford University, Stanford, CA 94305, USA
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Abstract
Whether prokaryotes (Bacteria and Archaea) are naturally organized into phenotypically and genetically cohesive units comparable to animal or plant species remains contested, frustrating attempts to estimate how many such units there might be, or to identify the ecological roles they play. Analyses of gene sequences in various closely related prokaryotic groups reveal that sequence diversity is typically organized into distinct clusters, and processes such as periodic selection and extensive recombination are understood to be drivers of cluster formation ("speciation"). However, observed patterns are rarely compared with those obtainable with simple null models of diversification under stochastic lineage birth and death and random genetic drift. Via a combination of simulations and analyses of core and phylogenetic marker genes, we show that patterns of diversity for the genera Escherichia, Neisseria, and Borrelia are generally indistinguishable from patterns arising under a null model. We suggest that caution should thus be taken in interpreting observed clustering as a result of selective evolutionary forces. Unknown forces do, however, appear to play a role in Helicobacter pylori, and some individual genes in all groups fail to conform to the null model. Taken together, we recommend the presented birth-death model as a null hypothesis in prokaryotic speciation studies. It is only when the real data are statistically different from the expectations under the null model that some speciation process should be invoked.
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Affiliation(s)
- Timothy J Straub
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755
| | - Olga Zhaxybayeva
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755;
- Department of Computer Science, Dartmouth College, Hanover, NH 03755
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