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Nhu NTK, Rahman MA, Goh KGK, Kim SJ, Phan MD, Peters KM, Alvarez-Fraga L, Hancock SJ, Ravi C, Kidd TJ, Sullivan MJ, Irvine KM, Beatson SA, Sweet MJ, Irwin AD, Vukovic J, Ulett GC, Hasnain SZ, Schembri MA. A convergent evolutionary pathway attenuating cellulose production drives enhanced virulence of some bacteria. Nat Commun 2024; 15:1441. [PMID: 38383596 PMCID: PMC10881479 DOI: 10.1038/s41467-024-45176-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Accepted: 01/16/2024] [Indexed: 02/23/2024] Open
Abstract
Bacteria adapt to selective pressure in their immediate environment in multiple ways. One mechanism involves the acquisition of independent mutations that disable or modify a key pathway, providing a signature of adaptation via convergent evolution. Extra-intestinal pathogenic Escherichia coli (ExPEC) belonging to sequence type 95 (ST95) represent a global clone frequently associated with severe human infections including acute pyelonephritis, sepsis, and neonatal meningitis. Here, we analysed a publicly available dataset of 613 ST95 genomes and identified a series of loss-of-function mutations that disrupt cellulose production or its modification in 55.3% of strains. We show the inability to produce cellulose significantly enhances ST95 invasive infection in a rat model of neonatal meningitis, leading to the disruption of intestinal barrier integrity in newborn pups and enhanced dissemination to the liver, spleen and brain. Consistent with these observations, disruption of cellulose production in ST95 augmented innate immune signalling and tissue neutrophil infiltration in a mouse model of urinary tract infection. Mutations that disrupt cellulose production were also identified in other virulent ExPEC STs, Shigella and Salmonella, suggesting a correlative association with many Enterobacteriaceae that cause severe human infection. Together, our findings provide an explanation for the emergence of hypervirulent Enterobacteriaceae clones.
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Affiliation(s)
- Nguyen Thi Khanh Nhu
- Institute for Molecular Bioscience (IMB), The University of Queensland, Brisbane, QLD, Australia
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia
| | - M Arifur Rahman
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia
- Immunopathology Group, Mater Research Institute, The University of Queensland, Translational Research Institute, Brisbane, Australia
- QIMR Berghofer Medical Research Institute, Brisbane QLD, Australia
| | - Kelvin G K Goh
- School of Pharmacy and Medical Sciences, Griffith University, Southport, QLD, Australia
- Menzies Health Institute Queensland, Griffith University, Southport, QLD, Australia
| | - Seung Jae Kim
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia
| | - Minh-Duy Phan
- Institute for Molecular Bioscience (IMB), The University of Queensland, Brisbane, QLD, Australia
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia
| | - Kate M Peters
- Institute for Molecular Bioscience (IMB), The University of Queensland, Brisbane, QLD, Australia
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia
| | - Laura Alvarez-Fraga
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia
- INRAE, Univ Montpellier, LBE, 102 Avenue des Etangs, Narbonne, 11100, France
| | - Steven J Hancock
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, UK
| | - Chitra Ravi
- Institute for Molecular Bioscience (IMB), The University of Queensland, Brisbane, QLD, Australia
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia
| | - Timothy J Kidd
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia
- Central Microbiology, Pathology Queensland, Royal Brisbane and Women's Hospital, Brisbane, Australia
| | - Matthew J Sullivan
- School of Pharmacy and Medical Sciences, Griffith University, Southport, QLD, Australia
- Menzies Health Institute Queensland, Griffith University, Southport, QLD, Australia
- School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Katharine M Irvine
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia
- Immunopathology Group, Mater Research Institute, The University of Queensland, Translational Research Institute, Brisbane, Australia
| | - Scott A Beatson
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia
| | - Matthew J Sweet
- Institute for Molecular Bioscience (IMB), The University of Queensland, Brisbane, QLD, Australia
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia
| | - Adam D Irwin
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia
- University of Queensland Centre for Clinical Research, Brisbane, Australia
- Queensland Children's Hospital, Brisbane, Australia
| | - Jana Vukovic
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia.
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia.
| | - Glen C Ulett
- School of Pharmacy and Medical Sciences, Griffith University, Southport, QLD, Australia.
- Menzies Health Institute Queensland, Griffith University, Southport, QLD, Australia.
| | - Sumaira Z Hasnain
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia.
- Immunopathology Group, Mater Research Institute, The University of Queensland, Translational Research Institute, Brisbane, Australia.
| | - Mark A Schembri
- Institute for Molecular Bioscience (IMB), The University of Queensland, Brisbane, QLD, Australia.
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia.
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia.
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Moinet M, Rogers L, Biggs P, Marshall J, Muirhead R, Devane M, Stott R, Cookson A. High-resolution genomic analysis to investigate the impact of the invasive brushtail possum (Trichosurus vulpecula) and other wildlife on microbial water quality assessments. PLoS One 2024; 19:e0295529. [PMID: 38236841 PMCID: PMC10796070 DOI: 10.1371/journal.pone.0295529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 11/21/2023] [Indexed: 01/22/2024] Open
Abstract
Escherichia coli are routine indicators of fecal contamination in water quality assessments. Contrary to livestock and human activities, brushtail possums (Trichosurus vulpecula), common invasive marsupials in Aotearoa/New Zealand, have not been thoroughly studied as a source of fecal contamination in freshwater. To investigate their potential role, Escherichia spp. isolates (n = 420) were recovered from possum gut contents and feces and were compared to those from water, soil, sediment, and periphyton samples, and from birds and other introduced mammals collected within the Mākirikiri Reserve, Dannevirke. Isolates were characterized using E. coli-specific real-time PCR targeting the uidA gene, Sanger sequencing of a partial gnd PCR product to generate a gnd sequence type (gST), and for 101 isolates, whole genome sequencing. Escherichia populations from 106 animal and environmental sample enrichments were analyzed using gnd metabarcoding. The alpha diversity of Escherichia gSTs was significantly lower in possums and animals compared with aquatic environmental samples, and some gSTs were shared between sample types, e.g., gST535 (in 85% of samples) and gST258 (71%). Forty percent of isolates gnd-typed and 75% of reads obtained by metabarcoding had gSTs shared between possums, other animals, and the environment. Core-genome single nucleotide polymorphism (SNP) analysis showed limited variation between several animal and environmental isolates (<10 SNPs). Our data show at an unprecedented scale that Escherichia clones are shared between possums, other wildlife, water, and the wider environment. These findings support the potential role of possums as contributors to fecal contamination in Aotearoa/New Zealand freshwater. Our study deepens the current knowledge of Escherichia populations in under-sampled wildlife. It presents a successful application of high-resolution genomic methods for fecal source tracking, thereby broadening the analytical toolbox available to water quality managers. Phylogenetic analysis of isolates and profiling of Escherichia populations provided useful information on the source(s) of fecal contamination and suggest that comprehensive invasive species management strategies may assist in restoring not only ecosystem health but also water health where microbial water quality is compromised.
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Affiliation(s)
- Marie Moinet
- Hopkirk Research Institute, AgResearch, Palmerston North, New Zealand
| | - Lynn Rogers
- Hopkirk Research Institute, AgResearch, Palmerston North, New Zealand
| | - Patrick Biggs
- mEpiLab, School of Veterinary Science, Massey University, Palmerston North, New Zealand
- School of Natural Sciences, Massey University, Palmerston North, New Zealand
| | - Jonathan Marshall
- School of Mathematical and Computational Sciences, Massey University, Palmerston North, New Zealand
| | | | - Megan Devane
- Institute of Environmental Science and Research Ltd. (ESR), Christchurch, New Zealand
| | - Rebecca Stott
- National Institute of Water and Atmospheric Research (NIWA), Hamilton, New Zealand
| | - Adrian Cookson
- Hopkirk Research Institute, AgResearch, Palmerston North, New Zealand
- mEpiLab, School of Veterinary Science, Massey University, Palmerston North, New Zealand
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3
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Lang C, Fruth A, Campbell IW, Jenkins C, Smith P, Strockbine N, Weill FX, Nübel U, Grad YH, Waldor MK, Flieger A. O-Antigen Diversification Masks Identification of Highly Pathogenic Shiga Toxin-Producing Escherichia coli O104:H4-Like Strains. Microbiol Spectr 2023; 11:e0098723. [PMID: 37212677 PMCID: PMC10269612 DOI: 10.1128/spectrum.00987-23] [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: 03/27/2023] [Accepted: 04/27/2023] [Indexed: 05/23/2023] Open
Abstract
Shiga toxin-producing Escherichia coli (STEC) can give rise to a range of clinical outcomes from diarrhea to the life-threatening systemic condition hemolytic-uremic syndrome (HUS). Although STEC O157:H7 is the serotype most frequently associated with HUS, a major outbreak of HUS occurred in 2011 in Germany and was caused by a rare serotype, STEC O104:H4. Prior to 2011 and since the outbreak, STEC O104:H4 strains have only rarely been associated with human infections. From 2012 to 2020, intensified STEC surveillance was performed in Germany where the subtyping of ~8,000 clinical isolates by molecular methods, including whole-genome sequencing, was carried out. A rare STEC serotype, O181:H4, associated with HUS was identified, and like the STEC O104:H4 outbreak strain, this strain belongs to sequence type 678 (ST678). Genomic and virulence comparisons revealed that the two strains are phylogenetically related and differ principally in the gene cluster encoding their respective lipopolysaccharide O-antigens but exhibit similar virulence phenotypes. In addition, five other serotypes belonging to ST678 from human clinical infection, such as OX13:H4, O127:H4, OgN-RKI9:H4, O131:H4, and O69:H4, were identified from diverse locations worldwide. IMPORTANCE Our data suggest that the high-virulence ensemble of the STEC O104:H4 outbreak strain remains a global threat because genomically similar strains cause disease worldwide but that the horizontal acquisition of O-antigen gene clusters has diversified the O-antigens of strains belonging to ST678. Thus, the identification of these highly pathogenic strains is masked by diverse and rare O-antigens, thereby confounding the interpretation of their potential risk.
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Affiliation(s)
- Christina Lang
- Division of Enteropathogenic Bacteria and Legionella, National Reference Centre for Salmonella and Other Enteric Bacterial Pathogens, Robert Koch Institut, Wernigerode, Germany
| | - Angelika Fruth
- Division of Enteropathogenic Bacteria and Legionella, National Reference Centre for Salmonella and Other Enteric Bacterial Pathogens, Robert Koch Institut, Wernigerode, Germany
| | - Ian W. Campbell
- Department of Microbiology, Division of Infectious Diseases, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Claire Jenkins
- Gastro and Food Safety (One Health) Division, Health Security Agency, London, United Kingdom
| | - Peyton Smith
- Division of Foodborne, Waterborne and Environmental Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Nancy Strockbine
- Division of Foodborne, Waterborne and Environmental Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - François-Xavier Weill
- Institut Pasteur, Université Paris Cité, Unité des Bactéries Pathogènes Entériques, Paris, France
| | - Ulrich Nübel
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
- German Center for Infection Research (DZIF), Partner Site Braunschweig-Hannover, Hannover, Germany
- Braunschweig Integrated Center of Systems Biology (BRICS), Technical University, Braunschweig, Germany
| | - Yonatan H. Grad
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Matthew K. Waldor
- Department of Microbiology, Division of Infectious Diseases, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, USA
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, Massachusetts, USA
- Howard Hughes Medical Institute, Boston, Massachusetts, USA
| | - Antje Flieger
- Division of Enteropathogenic Bacteria and Legionella, National Reference Centre for Salmonella and Other Enteric Bacterial Pathogens, Robert Koch Institut, Wernigerode, Germany
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Mejía L, Prado B, Cárdenas P, Trueba G, González-Candelas F. The impact of genetic recombination on pathogenic Leptospira. INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2022; 102:105313. [PMID: 35688386 DOI: 10.1016/j.meegid.2022.105313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 05/28/2022] [Accepted: 06/01/2022] [Indexed: 06/15/2023]
Abstract
Leptospirosis is the most common zoonosis worldwide, and is increasingly common in poor urban communities, where there is inadequate sewage disposal and abundance of domestic and peridomestic animals. There are many risk factors associated with the disease, such as contaminated water exposure, close contact with animals, floods, recreational activities related to water, wet agriculture. The symptoms of leptospirosis are common to other infectious diseases and, if not treated, it can lead to meningitis, liver failure, kidney damage and death. Leptospirosis is caused by 38 pathogenic species of Leptospira, which are divided in almost 30 serogroups and more than 300 serovars. The serological classification (serogroups and serovars) is based on the expression of distinct lipopolysaccharide (LPS) antigens. These antigens are also associated to protective immunity; antibodies against a serovar protect from any member of the same serovar. Serologic and phylogenetic analyses are not congruent probably due to genetic recombination of LPS genes among different leptospiral species. To analyze the importance of recombination in leptospiral evolution, we performed a gene-by-gene tree topology comparison on closed genomes available in public databases at two levels: among core genomes of pathogenic species (34 recombinant among 1213 core genes), and among core genomes of L. interrogans isolates (178/798). We found that most recombinant genes code for proteins involved in translation, ribosomal structure and biogenesis, but also for cell wall, membrane and envelope biogenesis. Besides, our final results showed that half of LPS genes are recombinant (18/36). This is relevant because serovar classification and vaccine development are based on these epitopes. The frequent recombination of LPS-associated genes suggests that natural selection is promoting the survival of recombinant lineages. These results may help understanding the factors that make Leptospira a successful pathogen.
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Affiliation(s)
- Lorena Mejía
- Instituto de Microbiología, Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito USFQ, Quito, Ecuador; Institute for Integrative Systems Biology, University of Valencia, Valencia, Spain; Joint Research Unit "Infection and Public Health" FISABIO-University of Valencia, Valencia, Spain
| | - Belén Prado
- Instituto de Microbiología, Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito USFQ, Quito, Ecuador
| | - Paúl Cárdenas
- Instituto de Microbiología, Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito USFQ, Quito, Ecuador
| | - Gabriel Trueba
- Instituto de Microbiología, Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito USFQ, Quito, Ecuador.
| | - Fernando González-Candelas
- Institute for Integrative Systems Biology, University of Valencia, Valencia, Spain; Joint Research Unit "Infection and Public Health" FISABIO-University of Valencia, Valencia, Spain; CIBER (Centro de Investigación Biomédica en Red) in Epidemiology and Public Health, Valencia, Spain.
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5
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Reid CJ, Cummins ML, Börjesson S, Brouwer MSM, Hasman H, Hammerum AM, Roer L, Hess S, Berendonk T, Nešporová K, Haenni M, Madec JY, Bethe A, Michael GB, Schink AK, Schwarz S, Dolejska M, Djordjevic SP. A role for ColV plasmids in the evolution of pathogenic Escherichia coli ST58. Nat Commun 2022; 13:683. [PMID: 35115531 PMCID: PMC8813906 DOI: 10.1038/s41467-022-28342-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 01/11/2022] [Indexed: 12/15/2022] Open
Abstract
Escherichia coli ST58 has recently emerged as a globally disseminated uropathogen that often progresses to sepsis. Unlike most pandemic extra-intestinal pathogenic E. coli (ExPEC), which belong to pathogenic phylogroup B2, ST58 belongs to the environmental/commensal phylogroup B1. Here, we present a pan-genomic analysis of a global collection of 752 ST58 isolates from diverse sources. We identify a large ST58 sub-lineage characterized by near ubiquitous carriage of ColV plasmids, which carry genes encoding virulence factors, and by a distinct accessory genome including genes typical of the Yersiniabactin High Pathogenicity Island. This sub-lineage includes three-quarters of all ExPEC sequences in our study and has a broad host range, although poultry and porcine sources predominate. By contrast, strains isolated from cattle often lack ColV plasmids. Our data indicate that ColV plasmid acquisition contributed to the divergence of the major ST58 sub-lineage, and different sub-lineages inhabit poultry, swine and cattle.
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Affiliation(s)
- Cameron J Reid
- iThree Institute, University of Technology Sydney, Ultimo, NSW, 2007, Australia.
| | - Max L Cummins
- iThree Institute, University of Technology Sydney, Ultimo, NSW, 2007, Australia
| | - Stefan Börjesson
- Department of Animal Health and Antimicrobial Strategies, National Veterinary Institute (SVA), 75189, Uppsala, Sweden
- Department of Microbiology, Public Health Agency of Sweden, 17182, Solna, Sweden
| | | | - Henrik Hasman
- Department of Bacteria, Parasites and Fungi, Statens Serum Institut, Copenhagen S, Denmark
| | - Anette M Hammerum
- Department of Bacteria, Parasites and Fungi, Statens Serum Institut, Copenhagen S, Denmark
| | - Louise Roer
- Department of Bacteria, Parasites and Fungi, Statens Serum Institut, Copenhagen S, Denmark
| | - Stefanie Hess
- Institute of Microbiology, Technische Universität Dresden, Dresden, Germany
| | - Thomas Berendonk
- Institute of Hydrobiology, Technische Universität Dresden, Dresden, Germany
| | - Kristina Nešporová
- CEITEC VETUNI, University of Veterinary Sciences Brno, Brno, Czech Republic
- Department of Biology and Wildlife Disease, Faculty of Veterinary Hygiene and Ecology, University of Veterinary Sciences Brno, Brno, Czech Republic
| | - Marisa Haenni
- Université de Lyon-ANSES, Unité Antibiorésistance et Virulence Bactériennes, Lyon, France
| | - Jean-Yves Madec
- Université de Lyon-ANSES, Unité Antibiorésistance et Virulence Bactériennes, Lyon, France
| | - Astrid Bethe
- Institute of Microbiology and Epizootics, Centre for Infection Medicine, Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
- Veterinary Centre for Resistance Research (TZR), Freie Universität Berlin, 14163, Berlin, Germany
| | - Geovana B Michael
- Institute of Microbiology and Epizootics, Centre for Infection Medicine, Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
- Veterinary Centre for Resistance Research (TZR), Freie Universität Berlin, 14163, Berlin, Germany
| | - Anne-Kathrin Schink
- Institute of Microbiology and Epizootics, Centre for Infection Medicine, Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
- Veterinary Centre for Resistance Research (TZR), Freie Universität Berlin, 14163, Berlin, Germany
| | - Stefan Schwarz
- Institute of Microbiology and Epizootics, Centre for Infection Medicine, Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
- Veterinary Centre for Resistance Research (TZR), Freie Universität Berlin, 14163, Berlin, Germany
| | - Monika Dolejska
- CEITEC VETUNI, University of Veterinary Sciences Brno, Brno, Czech Republic
- Department of Biology and Wildlife Disease, Faculty of Veterinary Hygiene and Ecology, University of Veterinary Sciences Brno, Brno, Czech Republic
- Biomedical Center, Charles University, Charles, Czech Republic
| | - Steven P Djordjevic
- iThree Institute, University of Technology Sydney, Ultimo, NSW, 2007, Australia.
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Dimopoulou M, Dols-Lafargue M. Exopolysaccharides Producing Lactic Acid Bacteria in Wine and Other Fermented Beverages: For Better or for Worse? Foods 2021; 10:2204. [PMID: 34574312 PMCID: PMC8466591 DOI: 10.3390/foods10092204] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 09/12/2021] [Accepted: 09/15/2021] [Indexed: 11/21/2022] Open
Abstract
Lactic acid bacteria (LAB) from fermented beverages such as wine, cider and beer produce a wide range of exopolysaccharides (EPS) through multiple biosynthetic pathways. These extracellular polysaccharides constitute key elements for bacterial species adaptation to such anthropic processes. In the food industry, LAB polysaccharides have been widely studied for their rheological, functional and nutritional properties; however, these have been poorly studied in wine, beer and cider until recently. In this review, we have gathered the information available on these specific polysaccharide structure and, biosynthetic pathways, as well as the physiology of their production. The genes associated with EPS synthesis are also presented and compared. Finally, the possible role of EPS for bacterial survival and spread, as well as the risks or possible benefits for the winemaker and the wine lover, are discussed.
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Affiliation(s)
- Maria Dimopoulou
- Department of Wine, Vine and Beverage Sciences, School of Food Science, University of West Attica, Ag. Spyridonos str, Egaleo, 12243 Athens, Greece;
| | - Marguerite Dols-Lafargue
- Unité de Recherche Œnologie EA 4577, University of Bordeaux, ISVV, USC 1366 INRA, Bordeaux INP, F-33140 Villenave d’Ornon, France
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7
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D'Aeth JC, van der Linden MPG, McGee L, de Lencastre H, Turner P, Song JH, Lo SW, Gladstone RA, Sá-Leão R, Ko KS, Hanage WP, Breiman RF, Beall B, Bentley SD, Croucher NJ. The role of interspecies recombination in the evolution of antibiotic-resistant pneumococci. eLife 2021; 10:e67113. [PMID: 34259624 PMCID: PMC8321556 DOI: 10.7554/elife.67113] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 04/16/2021] [Indexed: 12/27/2022] Open
Abstract
Multidrug-resistant Streptococcus pneumoniae emerge through the modification of core genome loci by interspecies homologous recombinations, and acquisition of gene cassettes. Both occurred in the otherwise contrasting histories of the antibiotic-resistant S. pneumoniae lineages PMEN3 and PMEN9. A single PMEN3 clade spread globally, evading vaccine-induced immunity through frequent serotype switching, whereas locally circulating PMEN9 clades independently gained resistance. Both lineages repeatedly integrated Tn916-type and Tn1207.1-type elements, conferring tetracycline and macrolide resistance, respectively, through homologous recombination importing sequences originating in other species. A species-wide dataset found over 100 instances of such interspecific acquisitions of resistance cassettes and flanking homologous arms. Phylodynamic analysis of the most commonly sampled Tn1207.1-type insertion in PMEN9, originating from a commensal and disrupting a competence gene, suggested its expansion across Germany was driven by a high ratio of macrolide-to-β-lactam consumption. Hence, selection from antibiotic consumption was sufficient for these atypically large recombinations to overcome species boundaries across the pneumococcal chromosome.
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Affiliation(s)
- Joshua C D'Aeth
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College LondonLondonUnited Kingdom
| | - Mark PG van der Linden
- Institute for Medical Microbiology, National Reference Center for Streptococci, University Hospital RWTH AachenAachenGermany
| | - Lesley McGee
- Respiratory Diseases Branch, Centers for Disease Control and PreventionAtlantaUnited States
| | - Herminia de Lencastre
- Laboratory of Molecular Genetics, Instituto de Tecnologia Química e Biológica, Universidade Nova de LisboaOeirasPortugal
- Laboratory of Microbiology and Infectious Diseases, The Rockefeller UniversityNew YorkUnited States
| | - Paul Turner
- Cambodia Oxford Medical Research Unit, Angkor Hospital for ChildrenSiem ReapCambodia
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of OxfordOxfordUnited Kingdom
| | - Jae-Hoon Song
- Department of Molecular Cell Biology, Sungkyunkwan University School of MedicineSuwonRepublic of Korea
| | - Stephanie W Lo
- Parasites & Microbes, Wellcome Sanger Institute, Wellcome Genome CampusHinxtonUnited Kingdom
| | - Rebecca A Gladstone
- Parasites & Microbes, Wellcome Sanger Institute, Wellcome Genome CampusHinxtonUnited Kingdom
| | - Raquel Sá-Leão
- Laboratory of Molecular Microbiology of Human Pathogens, Instituto de Tecnologia Química e Biológica, Universidade Nova de LisboaOeirasPortugal
| | - Kwan Soo Ko
- Department of Molecular Cell Biology, Sungkyunkwan University School of MedicineSuwonRepublic of Korea
| | - William P Hanage
- Center for Communicable Disease Dynamics, Harvard T.H. Chan School of Public HealthBostonUnited States
| | - Robert F Breiman
- Department of Global Health, Rollins School of Public Health, Emory UniversityAtlantaUnited States
| | - Bernard Beall
- Respiratory Diseases Branch, Centers for Disease Control and PreventionAtlantaUnited States
| | - Stephen D Bentley
- Parasites & Microbes, Wellcome Sanger Institute, Wellcome Genome CampusHinxtonUnited Kingdom
| | - Nicholas J Croucher
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College LondonLondonUnited Kingdom
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8
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Abstract
Escherichia coli is a commensal of the vertebrate gut that is increasingly involved in various intestinal and extra-intestinal infections as an opportunistic pathogen. Numerous pathotypes that represent groups of strains with specific pathogenic characteristics have been described based on heterogeneous and complex criteria. The democratization of whole-genome sequencing has led to an accumulation of genomic data that render possible a population phylogenomic approach to the emergence of virulence. Few lineages are responsible for the pathologies compared with the diversity of commensal strains. These lineages emerged multiple times during E. coli evolution, mainly by acquiring virulence genes located on mobile elements, but in a specific chromosomal phylogenetic background. This repeated emergence of stable and cosmopolitan lineages argues for an optimization of strain fitness through epistatic interactions between the virulence determinants and the remaining genome.
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9
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gndDb, a Database of Partial gnd Sequences To Assist with Analysis of Escherichia coli Communities Using High-Throughput Sequencing. Microbiol Resour Announc 2019; 8:8/33/e00476-19. [PMID: 31416858 PMCID: PMC6696633 DOI: 10.1128/mra.00476-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
The use of culture methods to detect Escherichia coli diversity does not provide sufficient resolution to identify strains present at low levels. Here, we target the hypervariable gnd gene and describe a database containing 534 distinct partial gnd sequences and associated O groups for use with culture-independent E. coli community analysis. The use of culture methods to detect Escherichia coli diversity does not provide sufficient resolution to identify strains present at low levels. Here, we target the hypervariable gnd gene and describe a database containing 534 distinct partial gnd sequences and associated O groups for use with culture-independent E. coli community analysis.
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Mostowy RJ, Holt KE. Diversity-Generating Machines: Genetics of Bacterial Sugar-Coating. Trends Microbiol 2018; 26:1008-1021. [PMID: 30037568 PMCID: PMC6249986 DOI: 10.1016/j.tim.2018.06.006] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 06/08/2018] [Accepted: 06/22/2018] [Indexed: 12/11/2022]
Abstract
Bacterial pathogens and commensals are surrounded by diverse surface polysaccharides which include capsules and lipopolysaccharides. These carbohydrates play a vital role in bacterial ecology and interactions with the environment. Here, we review recent rapid advancements in this field, which have improved our understanding of the roles, structures, and genetics of bacterial polysaccharide antigens. Genetic loci encoding the biosynthesis of these antigens may have evolved as bacterial diversity-generating machines, driven by selection from a variety of forces, including host immunity, bacteriophages, and cell-cell interactions. We argue that the high adaptive potential of polysaccharide antigens should be taken into account in the design of polysaccharide-targeting medical interventions like conjugate vaccines and phage-based therapies.
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Affiliation(s)
- Rafał J Mostowy
- Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, UK.
| | - Kathryn E Holt
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria, Australia; The London School of Hygiene and Tropical Medicine, London, United Kingdom
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11
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Cookson AL, Biggs PJ, Marshall JC, Reynolds A, Collis RM, French NP, Brightwell G. Culture independent analysis using gnd as a target gene to assess Escherichia coli diversity and community structure. Sci Rep 2017; 7:841. [PMID: 28404985 PMCID: PMC5429811 DOI: 10.1038/s41598-017-00890-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Accepted: 03/16/2017] [Indexed: 01/09/2023] Open
Abstract
Current culture methods to investigate changes in Escherichia coli community structure are often slow and laborious. Genes such as gnd (6-phosphogluconate dehydrogenase) have a highly variable nucleotide sequence and may provide a target for E. coli microbiome analysis using culture-independent methods. Metabarcoded PCR primers were used to generate separate libraries from calf faecal samples for high throughput sequencing. Although a total of 348 separate gnd sequence types (gSTs) were identified, 188 were likely to be due to sequencing errors. Of the remaining 160 gSTs, 92 did not match those in a database of 319 separate gnd sequences. ‘Animal’ was the main determinant of E. coli diversity with limited impact of sample type or DNA extraction method on intra-host E. coli community variation from faeces and recto-anal mucosal swab samples. This culture-independent study has addressed the difficulties of quantifying bacterial intra-species diversity and revealed that, whilst individual animals may harbour >50 separate E. coli strains, communities are dominated by <10 strains alongside a large pool of subdominant strains present at low abundances. This method will be useful for characterising the diversity and population structure of E. coli in experimental studies designed to assess the impact of interventions on the gut microbiome.
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Affiliation(s)
- Adrian L Cookson
- AgResearch Limited, Hopkirk Research Institute, Palmerston North, New Zealand. .,mEpiLab, Hopkirk Research Institute, Massey University, Palmerston North, New Zealand.
| | - Patrick J Biggs
- mEpiLab, Hopkirk Research Institute, Massey University, Palmerston North, New Zealand.,Massey Genome Service, New Zealand Genomics Limited, Massey University, Palmerston North, New Zealand
| | - Jonathan C Marshall
- mEpiLab, Hopkirk Research Institute, Massey University, Palmerston North, New Zealand.,Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Angela Reynolds
- AgResearch Limited, Hopkirk Research Institute, Palmerston North, New Zealand
| | - Rose M Collis
- AgResearch Limited, Hopkirk Research Institute, Palmerston North, New Zealand
| | - Nigel P French
- mEpiLab, Hopkirk Research Institute, Massey University, Palmerston North, New Zealand
| | - Gale Brightwell
- AgResearch Limited, Hopkirk Research Institute, Palmerston North, New Zealand
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Jeong H, Sim YM, Kim HJ, Lee SJ. Unveiling the Hybrid Genome Structure of Escherichia coli RR1 (HB101 RecA +). Front Microbiol 2017; 8:585. [PMID: 28421066 PMCID: PMC5379014 DOI: 10.3389/fmicb.2017.00585] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2017] [Accepted: 03/21/2017] [Indexed: 01/26/2023] Open
Abstract
There have been extensive genome sequencing studies for Escherichia coli strains, particularly for pathogenic isolates, because fast determination of pathogenic potential and/or drug resistance and their propagation routes is crucial. For laboratory E. coli strains, however, genome sequence information is limited except for several well-known strains. We determined the complete genome sequence of laboratory E. coli strain RR1 (HB101 RecA+), which has long been used as a general cloning host. A hybrid genome sequence of K-12 MG1655 and B BL21(DE3) was constructed based on the initial mapping of Illumina HiSeq reads to each reference, and iterative rounds of read mapping, variant detection, and consensus extraction were carried out. Finally, PCR and Sanger sequencing-based finishing were applied to resolve non-single nucleotide variant regions with aberrant read depths and breakpoints, most of them resulting from prophages and insertion sequence transpositions that are not present in the reference genome sequence. We found that 96.9% of the RR1 genome is derived from K-12, and identified exact crossover junctions between K-12 and B genomic fragments. However, because RR1 has experienced a series of genetic manipulations since branching from the common ancestor, it has a set of mutations different from those found in K-12 MG1655. As well as identifying all known genotypes of RR1 on the basis of genomic context, we found novel mutations. Our results extend current knowledge of the genotype of RR1 and its relatives, and provide insights into the pedigree, genomic background, and physiology of common laboratory strains.
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Affiliation(s)
- Haeyoung Jeong
- Infectious Disease Research Center, Korea Research Institute of Bioscience and BiotechnologyDaejeon, South Korea.,Biosystems and Bioengineering Program, University of Science and TechnologyDaejeon, South Korea
| | - Young Mi Sim
- Korean Bioinformation Center, Korea Research Institute of Bioscience and BiotechnologyDaejeon, South Korea
| | - Hyun Ju Kim
- Biosystems and Bioengineering Program, University of Science and TechnologyDaejeon, South Korea
| | - Sang Jun Lee
- Department of Systems Biotechnology, Chung-Ang UniversityAnseong, South Korea
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Kenyon JJ, Cunneen MM, Reeves PR. Genetics and evolution of Yersinia pseudotuberculosis O-specific polysaccharides: a novel pattern of O-antigen diversity. FEMS Microbiol Rev 2017; 41:200-217. [PMID: 28364730 PMCID: PMC5399914 DOI: 10.1093/femsre/fux002] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 02/02/2017] [Indexed: 11/29/2022] Open
Abstract
O-antigen polysaccharide is a major immunogenic feature of the lipopolysaccharide of Gram-negative bacteria, and most species produce a large variety of forms that differ substantially from one another. There are 18 known O-antigen forms in the Yersinia pseudotuberculosis complex, which are typical in being composed of multiple copies of a short oligosaccharide called an O unit. The O-antigen gene clusters are located between the hemH and gsk genes, and are atypical as 15 of them are closely related, each having one of five downstream gene modules for alternative main-chain synthesis, and one of seven upstream modules for alternative side-branch sugar synthesis. As a result, many of the genes are in more than one gene cluster. The gene order in each module is such that, in general, the earlier a gene product functions in O-unit synthesis, the closer the gene is to the 5΄ end for side-branch modules or the 3΄ end for main-chain modules. We propose a model whereby natural selection could generate the observed pattern in gene order, a pattern that has also been observed in other species.
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Affiliation(s)
- Johanna J. Kenyon
- School of Molecular Bioscience, The University of Sydney, Sydney, NSW 2006, Australia
- Institute of Health and Biomedical Innovation, Queensland University of Technology. Brisbane, QLD 4001, Australia
| | - Monica M. Cunneen
- School of Molecular Bioscience, The University of Sydney, Sydney, NSW 2006, Australia
| | - Peter R. Reeves
- School of Molecular Bioscience, The University of Sydney, Sydney, NSW 2006, Australia
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Abstract
The emergence of genomics over the last 10 years has provided new insights into the evolution and virulence of extraintestinal Escherichia coli. By combining population genetics and phylogenetic approaches to analyze whole-genome sequences, it became possible to link genomic features to specific phenotypes, such as the ability to cause urinary tract infections. An E. coli chromosome can vary extensively in length, ranging from 4.3 to 6.2 Mb, encoding 4,084 to 6,453 proteins. This huge diversity is structured as a set of less than 2,000 genes (core genome) that are conserved between all the strains and a set of variable genes. Based on the core genome, the history of the species can be reliably reconstructed, revealing the recent emergence of phylogenetic groups A and B1 and the more ancient groups B2, F, and D. Urovirulence is most often observed in B2/F/D group strains and is a multigenic process involving numerous combinations of genes and specific alleles with epistatic interactions, all leading down multiple evolutionary paths. The genes involved mainly code for adhesins, toxins, iron capture systems, and protectins, as well as metabolic pathways and mutation-rate-control systems. However, the barrier between commensal and uropathogenic E. coli strains is difficult to draw as the factors that are responsible for virulence have probably also been selected to allow survival of E. coli as a commensal in the intestinal tract. Genomic studies have also demonstrated that infections are not the result of a unique and stable isolate, but rather often involve several isolates with variable levels of diversity that dynamically changes over time.
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Abstract
We have examined a collection of the free-living marine bacterium Alteromonas genomes with cores diverging in average nucleotide identities ranging from 99.98% to 73.35%, i.e., from microbes that can be considered members of a natural clone (like in a clinical epidemiological outbreak) to borderline genus level. The genomes were largely syntenic allowing a precise delimitation of the core and flexible regions in each. The core was 1.4 Mb (ca. 30% of the typical strain genome size). Recombination rates along the core were high among strains belonging to the same species (37.7-83.7% of all nucleotide polymorphisms) but they decreased sharply between species (18.9-5.1%). Regarding the flexible genome, its main expansion occurred within the boundaries of the species, i.e., strains of the same species already have a large and diverse flexible genome. Flexible regions occupy mostly fixed genomic locations. Four large genomic islands are involved in the synthesis of strain-specific glycosydic receptors that we have called glycotypes. These genomic regions are exchanged by homologous recombination within and between species and there is evidence for their import from distant taxonomic units (other genera within the family). In addition, several hotspots for integration of gene cassettes by illegitimate recombination are distributed throughout the genome. They code for features that give each clone specific properties to interact with their ecological niche and must flow fast throughout the whole genus as they are found, with nearly identical sequences, in different species. Models for the generation of this genomic diversity involving phage predation are discussed.
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Affiliation(s)
- Mario López-Pérez
- Evolutionary Genomics Group, Departamento de Producción Vegetal y Microbiología, Universidad Miguel Hernández, Alicante, Spain
| | - Francisco Rodriguez-Valera
- Evolutionary Genomics Group, Departamento de Producción Vegetal y Microbiología, Universidad Miguel Hernández, Alicante, Spain
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Atzinger A, Butela K, Lawrence JG. The O-antigen mediates differential survival of Salmonella against communities of natural predators. MICROBIOLOGY-SGM 2016; 162:610-621. [PMID: 26888189 DOI: 10.1099/mic.0.000259] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Antigenically distinct members of bacterial species can be differentially distributed in the environment. Predators known to consume antigenically distinct prey with different efficiencies are also differentially distributed. Here we show that antigenically distinct, but otherwise isogenic and physiologically indistinct, strains of Salmonella enterica show differential survival in natural soil, sediment and intestinal environments, where they would face a community of predators. Decline in overall cell numbers is attenuated by factors that inhibit the action of predators, including heat and antiprotozoal and antihelminthic drugs. Moreover, the fitness of strains facing these predators - calculated by comparing survival with and without treatments attenuating predator activity - varies between environments. These results suggest that relative survival in natural environments is arbitrated by communities of natural predators whose feeding preferences, if not species composition, vary between environments. These data support the hypothesis that survival against natural predators may drive the differential distribution of bacteria among microenvironments.
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Affiliation(s)
- Aletheia Atzinger
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Kristen Butela
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Jeffrey G Lawrence
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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Molecular Characterization of Human Atypical Sorbitol-Fermenting Enteropathogenic Escherichia coli O157 Reveals High Diversity. J Clin Microbiol 2016; 54:1357-63. [PMID: 26984976 DOI: 10.1128/jcm.02897-15] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 03/07/2016] [Indexed: 12/19/2022] Open
Abstract
Alongside the well-characterized enterohemorrhagic Escherichia coli (EHEC) O157:H7, serogroup O157 comprises sorbitol-fermenting typical and atypical enteropathogenic E. coli (EPEC/aEPEC) strains that carry the intimin-encoding gene eae but not Shiga toxin-encoding genes (stx). Since little is known about these pathogens, we characterized 30 clinical isolates from patients with hemolytic uremic syndrome (HUS) or uncomplicated diarrhea with respect to their flagellin gene (fliC) type and multilocus sequence type (MLST). Moreover, we applied whole-genome sequencing (WGS) to determine the phylogenetic relationship with other eae-positive EHEC serotypes and the composition of the rfbO157 region. fliC typing resulted in five fliC types (H7, H16, H34, H39, and H45). Isolates of each fliC type shared a unique ST. In comparison to the 42 HUS-associated E. coli (HUSEC) strains, only the stx-negative isolates with fliCH7 shared their ST with EHEC O157:H7/H(-) strains. With the exception of one O157:H(-) fliCH16 isolate, HUS was exclusively associated with fliCH7. WGS corroborated the separation of the fliCH7 isolates, which were closely related to the EHEC O157:H7/H(-) isolates, and the diverse group of isolates exhibiting different fliC types, indicating independent evolution of the different serotypes. This was also supported by the heterogeneity within the rfbO157 region that exhibited extensive recombinations. The genotypic subtypes and distribution of clinical symptoms suggested that the stx-negative O157 strains with fliCH7 were originally EHEC strains that lost stx The remaining isolates form a distinct and diverse group of atypical EPEC isolates that do not possess the full spectrum of virulence genes, underlining the importance of identifying the H antigen for clinical risk assessment.
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Abstract
Bacteria reproduce asexually and pass on a single genome copied from the parent, a reproductive mode that assures the clonal descent of progeny; however, a truly clonal bacterial species is extremely rare. The signal of clonality can be interrupted by gene uptake and exchange, initiating homologous recombination that results in the unique sequence of one clone being incorporated into another. Because recombination occurs sporadically and on local scales, these events are often difficult to recognize, even when considering large samples of completely sequenced genomes. Moreover, several processes can produce the appearance of clonality in populations that undergo frequent recombination. The rates and consequences of recombination have been studied in Escherichia coli for over 40 y, and, during this time, there have been several shifting views of its clonal status, population structure, and rates of gene exchange. We reexamine the studies and retrace the evolution of the methods that have assessed the extent of DNA flux, largely focusing on its impact on the E. coli genome.
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Kingston AW, Roussel-Rossin C, Dupont C, Raleigh EA. Novel recA-Independent Horizontal Gene Transfer in Escherichia coli K-12. PLoS One 2015; 10:e0130813. [PMID: 26162088 PMCID: PMC4498929 DOI: 10.1371/journal.pone.0130813] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Accepted: 05/27/2015] [Indexed: 01/19/2023] Open
Abstract
In bacteria, mechanisms that incorporate DNA into a genome without strand-transfer proteins such as RecA play a major role in generating novelty by horizontal gene transfer. We describe a new illegitimate recombination event in Escherichia coli K-12: RecA-independent homologous replacements, with very large (megabase-length) donor patches replacing recipient DNA. A previously uncharacterized gene (yjiP) increases the frequency of RecA-independent replacement recombination. To show this, we used conjugal DNA transfer, combining a classical conjugation donor, HfrH, with modern genome engineering methods and whole genome sequencing analysis to enable interrogation of genetic dependence of integration mechanisms and characterization of recombination products. As in classical experiments, genomic DNA transfer begins at a unique position in the donor, entering the recipient via conjugation; antibiotic resistance markers are then used to select recombinant progeny. Different configurations of this system were used to compare known mechanisms for stable DNA incorporation, including homologous recombination, F'-plasmid formation, and genome duplication. A genome island of interest known as the immigration control region was specifically replaced in a minority of recombinants, at a frequency of 3 X 10(-12) CFU/recipient per hour.
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Affiliation(s)
- Anthony W. Kingston
- New England Biolabs, Ipswich, Massachusetts, 01938, United States of America
| | | | - Claire Dupont
- New England Biolabs, Ipswich, Massachusetts, 01938, United States of America
| | - Elisabeth A. Raleigh
- New England Biolabs, Ipswich, Massachusetts, 01938, United States of America
- * E-mail:
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Abstract
An approximation to the ∼4-Mbp basic genome shared by 32 strains of Escherichia coli representing six evolutionary groups has been derived and analyzed computationally. A multiple alignment of the 32 complete genome sequences was filtered to remove mobile elements and identify the most reliable ∼90% of the aligned length of each of the resulting 496 basic-genome pairs. Patterns of single base-pair mutations (SNPs) in aligned pairs distinguish clonally inherited regions from regions where either genome has acquired DNA fragments from diverged genomes by homologous recombination since their last common ancestor. Such recombinant transfer is pervasive across the basic genome, mostly between genomes in the same evolutionary group, and generates many unique mosaic patterns. The six least-diverged genome pairs have one or two recombinant transfers of length ∼40-115 kbp (and few if any other transfers), each containing one or more gene clusters known to confer strong selective advantage in some environments. Moderately diverged genome pairs (0.4-1% SNPs) show mosaic patterns of interspersed clonal and recombinant regions of varying lengths throughout the basic genome, whereas more highly diverged pairs within an evolutionary group or pairs between evolutionary groups having >1.3% SNPs have few clonal matches longer than a few kilobase pairs. Many recombinant transfers appear to incorporate fragments of the entering DNA produced by restriction systems of the recipient cell. A simple computational model can closely fit the data. Most recombinant transfers seem likely to be due to generalized transduction by coevolving populations of phages, which could efficiently distribute variability throughout bacterial genomes.
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Wang C, Sui Z, Leclercq SO, Zhang G, Zhao M, Chen W, Feng J. Functional characterization and phylogenetic analysis of acquired and intrinsic macrolide phosphotransferases in theBacillus cereusgroup. Environ Microbiol 2014; 17:1560-73. [DOI: 10.1111/1462-2920.12578] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Accepted: 07/21/2014] [Indexed: 11/29/2022]
Affiliation(s)
- Chao Wang
- State Key Laboratory of Microbial Resources; Institute of Microbiology; Chinese Academy of Sciences; Beijing 100101 China
| | - Zhihai Sui
- State Key Laboratory of Microbial Resources; Institute of Microbiology; Chinese Academy of Sciences; Beijing 100101 China
| | - Sébastien Olivier Leclercq
- State Key Laboratory of Microbial Resources; Institute of Microbiology; Chinese Academy of Sciences; Beijing 100101 China
| | - Gang Zhang
- State Key Laboratory of Microbial Resources; Institute of Microbiology; Chinese Academy of Sciences; Beijing 100101 China
| | - Meilin Zhao
- School of Food and Biological Engineering; Jiangsu University; Zhenjiang Jiangsu 212013 China
| | - Weiqi Chen
- Department of Environmental and Biological Pharmaceutical; Beijing Industrial Technician College; Beijing 100023 China
| | - Jie Feng
- State Key Laboratory of Microbial Resources; Institute of Microbiology; Chinese Academy of Sciences; Beijing 100101 China
- Beijing Key Laboratory of Microbial Drug Resistance and Resistome; Beijing 100101 China
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Genome-wide recombination drives diversification of epidemic strains of Acinetobacter baumannii. Proc Natl Acad Sci U S A 2011; 108:13758-63. [PMID: 21825119 DOI: 10.1073/pnas.1104404108] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Acinetobacter baumannii is an emerging human pathogen and a significant cause of nosocomial infections among hospital patients worldwide. The enormous increase in multidrug resistance among hospital isolates and the recent emergence of pan-drug-resistant strains underscores the urgency to understand how A. baumannii evolves in hospital environments. To this end, we undertook a genomic study of a polyclonal outbreak of multidrug-resistant A. baumannii at the research-based National Institutes of Health Clinical Center. Comparing the complete genome sequences of the three dominant outbreak strain types enabled us to conclude that, despite all belonging to the same epidemic lineage, the three strains diverged before their arrival at the National Institutes of Health. The simultaneous presence of three divergent strains from this lineage supports its increasing prevalence in international hospitals and suggests an ongoing adaptation to the hospital environment. Further genomic comparisons uncovered that much of the diversification that occurred since the divergence of the three outbreak strains was mediated by homologous recombination across 20% of their genomes. Inspection of recombinant regions revealed that several regions were associated with either the loss or swapping out of genes encoding proteins that are exposed to the cell surface or that synthesize cell-surface molecules. Extending our analysis to a larger set of international clinical isolates revealed a previously unappreciated ability of A. baumannii to vary surface molecules through horizontal gene transfer, with subsequent intraspecies dissemination by homologous recombination. These findings have immediate implications in surveillance, prevention, and treatment of A. baumannii infections.
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Screening of Escherichia coli species biodiversity reveals new biofilm-associated antiadhesion polysaccharides. mBio 2011; 2:e00043-11. [PMID: 21558434 PMCID: PMC3101779 DOI: 10.1128/mbio.00043-11] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial biofilms often form multispecies communities in which complex but ill-understood competition and cooperation interactions occur. In light of the profound physiological modifications associated with this lifestyle, we hypothesized that the biofilm environment might represent an untapped source of natural bioactive molecules interfering with bacterial adhesion or biofilm formation. We produced cell-free solutions extracted from in vitro mature biofilms formed by 122 natural Escherichia coli isolates, and we screened these biofilm extracts for antiadhesion molecules active on a panel of Gram-positive and Gram-negative bacteria. Using this approach, we showed that 20% of the tested biofilm extracts contained molecules that antagonize bacterial growth or adhesion. We characterized a compound, produced by a commensal animal E. coli strain, for which activity is detected only in biofilm extract. Biochemical and genetic analyses showed that this compound corresponds to a new type of released high-molecular-weight polysaccharide whose biofilm-associated production is regulated by the RfaH protein. We demonstrated that the antiadhesion activity of this polysaccharide was restricted to Gram-positive bacteria and that its production reduced susceptibility to invasion and provided rapid exclusion of Staphylococcus aureus from mixed E. coli and S. aureus biofilms. Our results therefore demonstrate that biofilms contain molecules that contribute to the dynamics of mixed bacterial communities and that are not or only poorly detected in unconcentrated planktonic supernatants. Systematic identification of these compounds could lead to strategies that limit pathogen surface colonization and reduce the burden associated with the development of bacterial biofilms on medical devices. We sought to demonstrate that bacterial biofilms are reservoirs for unknown molecules that antagonize bacterial adhesion. The use of natural strains representative of Escherichia coli species biodiversity showed that nonbiocidal antiadhesion polysaccharides are frequently found in mature biofilm extracts (bacterium-free suspensions which contain soluble molecules produced within the biofilm). Release of an antiadhesion polysaccharide confers a competitive advantage upon the producing strain against clinically relevant pathogens such as Staphylococcus aureus. Hence, exploring the biofilm environment provides a better understanding of bacterial interactions within complex communities and could lead to improved control of pathogen colonization.
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Ch'ng SL, Octavia S, Xia Q, Duong A, Tanaka MM, Fukushima H, Lan R. Population structure and evolution of pathogenicity of Yersinia pseudotuberculosis. Appl Environ Microbiol 2011; 77:768-75. [PMID: 21131531 PMCID: PMC3028722 DOI: 10.1128/aem.01993-10] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Accepted: 11/22/2010] [Indexed: 11/20/2022] Open
Abstract
Yersinia pseudotuberculosis is an enteric human pathogen but is widespread in the environment. Pathogenicity is determined by a number of virulence factors, including the virulence plasmid pYV, the high-pathogenicity island (HPI), and the Y. pseudotuberculosis-derived mitogen (YPM), a superantigen. The presence of the 3 virulence factors varies among Y. pseudotuberculosis isolates. We developed a multilocus sequence typing (MLST) scheme to address the population structure of Y. pseudotuberculosis and the evolution of its pathogenicity. The seven housekeeping genes selected for MLST were mdh, recA, sucA, fumC, aroC, pgi, and gyrB. An MLST analysis of 83 isolates of Y. pseudotuberculosis, representing 19 different serotypes and six different genetic groups, identified 61 sequence types (STs) and 12 clonal complexes. Out of 26 allelic changes that occurred in the 12 clonal complexes, 13 were mutational events while 13 were recombinational events, indicating that recombination and mutation contributed equally to the diversification of the clonal complexes. The isolates were separated into 2 distinctive clusters, A and B. Cluster A is the major cluster, with 53 STs (including Y. pestis strains), and is distributed worldwide, while cluster B is restricted to the Far East. The YPM gene is widely distributed on the phylogenetic tree, with ypmA in cluster A and ypmB in cluster B. pYV is present in cluster A only but is sporadically absent in some cluster A isolates. In contrast, an HPI is present only in a limited number of lineages and must be gained by lateral transfer. Three STs carry all 3 virulence factors and can be regarded as high-pathogenicity clones. Isolates from the same ST may not carry all 3 virulence factors, indicating frequent gain or loss of these factors. The differences in pathogenicity among Y. pseudotuberculosis strains are likely due to the variable presence and instability of the virulence factors.
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Affiliation(s)
- Shear Lane Ch'ng
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia, Shimane Prefectural Institute of Public Health and Environmental Science, 582-1 Nishihamasada, Matsue, Shimane 699-0122, Japan
| | - Sophie Octavia
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia, Shimane Prefectural Institute of Public Health and Environmental Science, 582-1 Nishihamasada, Matsue, Shimane 699-0122, Japan
| | - Qiuyu Xia
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia, Shimane Prefectural Institute of Public Health and Environmental Science, 582-1 Nishihamasada, Matsue, Shimane 699-0122, Japan
| | - An Duong
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia, Shimane Prefectural Institute of Public Health and Environmental Science, 582-1 Nishihamasada, Matsue, Shimane 699-0122, Japan
| | - Mark M. Tanaka
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia, Shimane Prefectural Institute of Public Health and Environmental Science, 582-1 Nishihamasada, Matsue, Shimane 699-0122, Japan
| | - Hiroshi Fukushima
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia, Shimane Prefectural Institute of Public Health and Environmental Science, 582-1 Nishihamasada, Matsue, Shimane 699-0122, Japan
| | - Ruiting Lan
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia, Shimane Prefectural Institute of Public Health and Environmental Science, 582-1 Nishihamasada, Matsue, Shimane 699-0122, Japan
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Archer CT, Kim JF, Jeong H, Park JH, Vickers CE, Lee SY, Nielsen LK. The genome sequence of E. coli W (ATCC 9637): comparative genome analysis and an improved genome-scale reconstruction of E. coli. BMC Genomics 2011; 12:9. [PMID: 21208457 PMCID: PMC3032704 DOI: 10.1186/1471-2164-12-9] [Citation(s) in RCA: 132] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Accepted: 01/06/2011] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Escherichia coli is a model prokaryote, an important pathogen, and a key organism for industrial biotechnology. E. coli W (ATCC 9637), one of four strains designated as safe for laboratory purposes, has not been sequenced. E. coli W is a fast-growing strain and is the only safe strain that can utilize sucrose as a carbon source. Lifecycle analysis has demonstrated that sucrose from sugarcane is a preferred carbon source for industrial bioprocesses. RESULTS We have sequenced and annotated the genome of E. coli W. The chromosome is 4,900,968 bp and encodes 4,764 ORFs. Two plasmids, pRK1 (102,536 bp) and pRK2 (5,360 bp), are also present. W has unique features relative to other sequenced laboratory strains (K-12, B and Crooks): it has a larger genome and belongs to phylogroup B1 rather than A. W also grows on a much broader range of carbon sources than does K-12. A genome-scale reconstruction was developed and validated in order to interrogate metabolic properties. CONCLUSIONS The genome of W is more similar to commensal and pathogenic B1 strains than phylogroup A strains, and therefore has greater utility for comparative analyses with these strains. W should therefore be the strain of choice, or 'type strain' for group B1 comparative analyses. The genome annotation and tools created here are expected to allow further utilization and development of E. coli W as an industrial organism for sucrose-based bioprocesses. Refinements in our E. coli metabolic reconstruction allow it to more accurately define E. coli metabolism relative to previous models.
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Affiliation(s)
- Colin T Archer
- Australian Institute for Bioengineering and Nanotechnology, Cnr Cooper and College Rds, The University of Queensland, St Lucia, Queensland 4072 Australia
| | - Jihyun F Kim
- Industrial Biotechnology and Bioenergy Research Center, Korea Research Institute of Bioscience and Biotechnology, 111 Gwahangno, Yuseong-gu, Daejeon, Korea
| | - Haeyoung Jeong
- Industrial Biotechnology and Bioenergy Research Center, Korea Research Institute of Bioscience and Biotechnology, 111 Gwahangno, Yuseong-gu, Daejeon, Korea
| | - Jin Hwan Park
- Department of Chemical and Biomolecular Engineering (BK21 program) and Center for Systems and Synthetic Biotechnology, Institute for the BioCentury, KAIST, 335 Gwahangno, Yuseong-gu, Daejeon 305-701, Republic of Korea
| | - Claudia E Vickers
- Australian Institute for Bioengineering and Nanotechnology, Cnr Cooper and College Rds, The University of Queensland, St Lucia, Queensland 4072 Australia
| | - Sang Yup Lee
- Department of Chemical and Biomolecular Engineering (BK21 program) and Center for Systems and Synthetic Biotechnology, Institute for the BioCentury, KAIST, 335 Gwahangno, Yuseong-gu, Daejeon 305-701, Republic of Korea
| | - Lars K Nielsen
- Australian Institute for Bioengineering and Nanotechnology, Cnr Cooper and College Rds, The University of Queensland, St Lucia, Queensland 4072 Australia
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Didelot X, Maiden MCJ. Impact of recombination on bacterial evolution. Trends Microbiol 2010; 18:315-22. [PMID: 20452218 PMCID: PMC3985120 DOI: 10.1016/j.tim.2010.04.002] [Citation(s) in RCA: 237] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2010] [Revised: 03/29/2010] [Accepted: 04/05/2010] [Indexed: 02/07/2023]
Abstract
Genetic exchange plays a defining role in the evolution of many bacteria. The recent accumulation of nucleotide sequence data from multiple members of diverse bacterial genera has facilitated comparative studies that have revealed many features of this process. Here we focus on genetic exchange that has involved homologous recombination and illustrate how nucleotide sequence data have furthered our understanding of: (i) the frequency of recombination; (ii) the impact of recombination in different parts of the genome; and (iii) patterns of gene flow within bacterial populations. Summarizing the results obtained for a range of bacteria, we survey evidence indicating that the extent and nature of recombination vary widely among microbiological species and often among lineages assigned to the same microbiological species. These results have important implications in studies ranging from epidemiological investigations to examination of the bacterial species problem.
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Affiliation(s)
- Xavier Didelot
- Department of Statistics, University of Warwick, Coventry, CV4 7AL, UK.
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Abstract
The primary habitat of Escherichia coli is the vertebrate gut, where it is the predominant aerobic organism, living in symbiosis with its host. Despite the occurrence of recombination events, the population structure is predominantly clonal, allowing the delineation of major phylogenetic groups. The genetic structure of commensal E. coli is shaped by multiple host and environmental factors, and the determinants involved in the virulence of the bacteria may in fact reflect adaptation to commensal habitats. A better characterization of the commensal niche is necessary to understand how a useful commensal can become a harmful pathogen. In this Review we describe the population structure of commensal E. coli, the factors involved in the spread of different strains, how the bacteria can adapt to different niches and how a commensal lifestyle can evolve into a pathogenic one.
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Derivation of Escherichia coli O157:H7 from its O55:H7 precursor. PLoS One 2010; 5:e8700. [PMID: 20090843 PMCID: PMC2806823 DOI: 10.1371/journal.pone.0008700] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Accepted: 12/14/2009] [Indexed: 11/25/2022] Open
Abstract
There are 29 E. coli genome sequences available, mostly related to studies of species diversity or mode of pathogenicity, including two genomes of the well-known O157:H7 clone. However, there have been no genome studies of closely related clones aimed at exposing the details of evolutionary change. Here we sequenced the genome of an O55:H7 strain, closely related to the major pathogenic O157:H7 clone, with published genome sequences, and undertook comparative genomic and proteomic analysis. We were able to allocate most differences between the genomes to individual mutations, recombination events, or lateral gene transfer events, in specific lineages. Major differences include a type II secretion system present only in the O55:H7 chromosome, fewer type III secretion system effectors in O55:H7, and 19 phage genomes or phagelike elements in O55:H7 compared to 23 in O157:H7, with only three common to both. Many other changes were found in both O55:H7 and O157:H7 lineages, but in general there has been more change in the O157:H7 lineages. For example, we found 50% more synonymous mutational substitutions in O157:H7 compared to O55:H7. The two strains also diverged at the proteomic level. Mutational synonymous SNPs were used to estimate a divergence time of 400 years using a new clock rate, in contrast to 14,000 to 70,000 years using the traditional clock rates. The same approaches were applied to three closely related extraintestinal pathogenic E. coli genomes, and similar levels of mutation and recombination were found. This study revealed for the first time the full range of events involved in the evolution of the O157:H7 clone from its O55:H7 ancestor, and suggested that O157:H7 arose quite recently. Our findings also suggest that E. coli has a much lower frequency of recombination relative to mutation than was observed in a comparable study of a Vibrio cholerae lineage.
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29
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Jeong H, Barbe V, Lee CH, Vallenet D, Yu DS, Choi SH, Couloux A, Lee SW, Yoon SH, Cattolico L, Hur CG, Park HS, Ségurens B, Kim SC, Oh TK, Lenski RE, Studier FW, Daegelen P, Kim JF. Genome sequences of Escherichia coli B strains REL606 and BL21(DE3). J Mol Biol 2009; 394:644-52. [PMID: 19786035 DOI: 10.1016/j.jmb.2009.09.052] [Citation(s) in RCA: 267] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Accepted: 09/21/2009] [Indexed: 12/23/2022]
Abstract
Escherichia coli K-12 and B have been the subjects of classical experiments from which much of our understanding of molecular genetics has emerged. We present here complete genome sequences of two E. coli B strains, REL606, used in a long-term evolution experiment, and BL21(DE3), widely used to express recombinant proteins. The two genomes differ in length by 72,304 bp and have 426 single base pair differences, a seemingly large difference for laboratory strains having a common ancestor within the last 67 years. Transpositions by IS1 and IS150 have occurred in both lineages. Integration of the DE3 prophage in BL21(DE3) apparently displaced a defective prophage in the lambda attachment site of B. As might have been anticipated from the many genetic and biochemical experiments comparing B and K-12 over the years, the B genomes are similar in size and organization to the genome of E. coli K-12 MG1655 and have >99% sequence identity over approximately 92% of their genomes. E. coli B and K-12 differ considerably in distribution of IS elements and in location and composition of larger mobile elements. An unexpected difference is the absence of a large cluster of flagella genes in B, due to a 41 kbp IS1-mediated deletion. Gene clusters that specify the LPS core, O antigen, and restriction enzymes differ substantially, presumably because of horizontal transfer. Comparative analysis of 32 independently isolated E. coli and Shigella genomes, both commensals and pathogenic strains, identifies a minimal set of genes in common plus many strain-specific genes that constitute a large E. coli pan-genome.
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Affiliation(s)
- Haeyoung Jeong
- Korea Research Institute of Bioscience and Biotechnology (KRIBB), 111 Gwahangno, Yuseong, Daejeon 305-806, Korea
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Studier FW, Daegelen P, Lenski RE, Maslov S, Kim JF. Understanding the differences between genome sequences of Escherichia coli B strains REL606 and BL21(DE3) and comparison of the E. coli B and K-12 genomes. J Mol Biol 2009; 394:653-80. [PMID: 19765592 DOI: 10.1016/j.jmb.2009.09.021] [Citation(s) in RCA: 147] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Revised: 09/09/2009] [Accepted: 09/10/2009] [Indexed: 11/20/2022]
Abstract
Each difference between the genome sequences of Escherichia coli B strains REL606 and BL21(DE3) can be interpreted in light of known laboratory manipulations plus a gene conversion between ribosomal RNA operons. Two treatments with 1-methyl-3-nitro-1-nitrosoguanidine in the REL606 lineage produced at least 93 single-base-pair mutations ( approximately 90% GC-to-AT transitions) and 3 single-base-pair GC deletions. Two UV treatments in the BL21(DE3) lineage produced only 4 single-base-pair mutations but 16 large deletions. P1 transductions from K-12 into the two B lineages produced 317 single-base-pair differences and 9 insertions or deletions, reflecting differences between B DNA in BL21(DE3) and integrated restriction fragments of K-12 DNA inherited by REL606. Two sites showed selective enrichment of spontaneous mutations. No unselected spontaneous single-base-pair mutations were evident. The genome sequences revealed that a progenitor of REL606 had been misidentified, explaining initially perplexing differences. Limited sequencing of other B strains defined characteristic properties of B and allowed assembly of the inferred genome of the ancestral B of Delbrück and Luria. Comparison of the B and K-12 genomes shows that more than half of the 3793 proteins of their basic genomes are predicted to be identical, although approximately 310 appear to be functional in either B or K-12 but not in both. The ancestral basic genome appears to have had approximately 4039 coding sequences occupying approximately 4.0 Mbp. Repeated horizontal transfer from diverged Escherichia coli genomes and homologous recombination may explain the observed variable distribution of single-base-pair differences. Fifteen sites are occupied by phage-related elements, but only six by comparable elements at the same site. More than 50 sites are occupied by IS elements in both B and K, 16 in common, and likely founding IS elements are identified. A signature of widespread cryptic phage P4-type mobile elements was identified. Complex deletions (dense clusters of small deletions and substitutions) apparently removed nonessential genes from approximately 30 sites in the basic genomes.
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Affiliation(s)
- F William Studier
- Biology Department, Brookhaven National Laboratory, PO Box 5000, Upton, NY 11973-5000, USA.
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31
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Shapiro BJ, David LA, Friedman J, Alm EJ. Looking for Darwin's footprints in the microbial world. Trends Microbiol 2009; 17:196-204. [PMID: 19375326 DOI: 10.1016/j.tim.2009.02.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2008] [Revised: 01/26/2009] [Accepted: 02/09/2009] [Indexed: 10/20/2022]
Abstract
As we observe the 200th anniversary of Charles Darwin's birth, microbiologists interested in the application of Darwin's ideas to the microscopic world have a lot to celebrate: an emerging picture of the (mostly microbial) Tree of Life at ever-increasing resolution, an understanding of horizontal gene transfer as a driving force in the evolution of microbes, and thousands of complete genome sequences to help formulate and refine our theories. At the same time, quantitative models of the microevolutionary processes shaping microbial populations remain just out of reach, a point that is perhaps most dramatically illustrated by the lack of consensus on how (or even whether) to define bacterial species. Here, we summarize progress and prospects in bacterial population genetics, with an emphasis on detecting the footprint of positive Darwinian selection in microbial genomes.
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Affiliation(s)
- B Jesse Shapiro
- Program in Computational and Systems Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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32
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Ilatovskiy A, Petukhov M. Genome-Wide Search for Local DNA Segments with Anomalous GC-Content. J Comput Biol 2009; 16:555-64. [DOI: 10.1089/cmb.2008.0159] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Andrey Ilatovskiy
- Division of Molecular and Radiation Biophysics, Petersburg Nuclear Physics Institute, Russian Academy of Sciences, Gatchina/St. Petersburg, and Research and Education Centre “Biophysics,” PNPI RAS and St. Petersburg State Polytecnic University, St. Petersburg, Russia
| | - Michael Petukhov
- Division of Molecular and Radiation Biophysics, Petersburg Nuclear Physics Institute, Russian Academy of Sciences, Gatchina/St. Petersburg, and Research and Education Centre “Biophysics,” PNPI RAS and St. Petersburg State Polytecnic University, St. Petersburg, Russia
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33
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Touchon M, Hoede C, Tenaillon O, Barbe V, Baeriswyl S, Bidet P, Bingen E, Bonacorsi S, Bouchier C, Bouvet O, Calteau A, Chiapello H, Clermont O, Cruveiller S, Danchin A, Diard M, Dossat C, Karoui ME, Frapy E, Garry L, Ghigo JM, Gilles AM, Johnson J, Le Bouguénec C, Lescat M, Mangenot S, Martinez-Jéhanne V, Matic I, Nassif X, Oztas S, Petit MA, Pichon C, Rouy Z, Ruf CS, Schneider D, Tourret J, Vacherie B, Vallenet D, Médigue C, Rocha EPC, Denamur E. Organised genome dynamics in the Escherichia coli species results in highly diverse adaptive paths. PLoS Genet 2009; 5:e1000344. [PMID: 19165319 PMCID: PMC2617782 DOI: 10.1371/journal.pgen.1000344] [Citation(s) in RCA: 778] [Impact Index Per Article: 51.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Accepted: 12/16/2008] [Indexed: 01/01/2023] Open
Abstract
The Escherichia coli species represents one of the best-studied model organisms, but also encompasses a variety of commensal and pathogenic strains that diversify by high rates of genetic change. We uniformly (re-) annotated the genomes of 20 commensal and pathogenic E. coli strains and one strain of E. fergusonii (the closest E. coli related species), including seven that we sequenced to completion. Within the ∼18,000 families of orthologous genes, we found ∼2,000 common to all strains. Although recombination rates are much higher than mutation rates, we show, both theoretically and using phylogenetic inference, that this does not obscure the phylogenetic signal, which places the B2 phylogenetic group and one group D strain at the basal position. Based on this phylogeny, we inferred past evolutionary events of gain and loss of genes, identifying functional classes under opposite selection pressures. We found an important adaptive role for metabolism diversification within group B2 and Shigella strains, but identified few or no extraintestinal virulence-specific genes, which could render difficult the development of a vaccine against extraintestinal infections. Genome flux in E. coli is confined to a small number of conserved positions in the chromosome, which most often are not associated with integrases or tRNA genes. Core genes flanking some of these regions show higher rates of recombination, suggesting that a gene, once acquired by a strain, spreads within the species by homologous recombination at the flanking genes. Finally, the genome's long-scale structure of recombination indicates lower recombination rates, but not higher mutation rates, at the terminus of replication. The ensuing effect of background selection and biased gene conversion may thus explain why this region is A+T-rich and shows high sequence divergence but low sequence polymorphism. Overall, despite a very high gene flow, genes co-exist in an organised genome. Although abundant knowledge has been accumulated regarding the E. coli laboratory strain K-12, little is known about the evolutionary trajectories that have driven the high diversity observed among natural isolates of the species, which encompass both commensal and highly virulent intestinal and extraintestinal pathogenic strains. We have annotated or re-annotated the genomes of 20 commensal and pathogenic E. coli strains and one strain of E. fergusonii (the closest E. coli related species), including seven that we sequenced to completion. Although recombination rates are much higher than mutation rates, we were able to reconstruct a robust phylogeny based on the ∼2,000 genes common to all strains. Based on this phylogeny, we established the evolutionary scenario of gains and losses of thousands of specific genes, identifying functional classes under opposite selection pressures. This genome flux is confined to very few positions in the chromosome, which are the same for every genome. Notably, we identified few or no extraintestinal virulence-specific genes. We also defined a long-scale structure of recombination in the genome with lower recombination rates at the terminus of replication. These findings demonstrate that, despite a very high gene flow, genes can co-exist in an organised genome.
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Affiliation(s)
- Marie Touchon
- Atelier de BioInformatique, Université Pierre et Marie Curie - Paris 6 (UPMC), Paris, France
- Microbial Evolutionary Genomics, Institut Pasteur, CNRS URA2171, Paris, France
| | - Claire Hoede
- Faculté de Médecine, Université Paris 7 Denis Diderot, INSERM U722, Site Xavier Bichat, Paris, France
| | - Olivier Tenaillon
- Faculté de Médecine, Université Paris 7 Denis Diderot, INSERM U722, Site Xavier Bichat, Paris, France
| | | | - Simon Baeriswyl
- Faculté de Médecine, Université Paris 5 René Descartes, INSERM U571, Paris, France
| | - Philippe Bidet
- Université Paris 7 Denis Diderot, Hôpital Robert Debré (APHP), EA 3105, Paris, France
| | - Edouard Bingen
- Université Paris 7 Denis Diderot, Hôpital Robert Debré (APHP), EA 3105, Paris, France
| | - Stéphane Bonacorsi
- Université Paris 7 Denis Diderot, Hôpital Robert Debré (APHP), EA 3105, Paris, France
| | | | - Odile Bouvet
- Faculté de Médecine, Université Paris 7 Denis Diderot, INSERM U722, Site Xavier Bichat, Paris, France
| | - Alexandra Calteau
- Laboratoire de Génomique Comparative, CNRS UMR8030, Institut de Génomique, CEA, Génoscope, Evry, France
| | - Hélène Chiapello
- UR1077 Mathématique, Informatique, et Génome, INRA, Jouy en Josas, France
| | - Olivier Clermont
- Faculté de Médecine, Université Paris 7 Denis Diderot, INSERM U722, Site Xavier Bichat, Paris, France
| | - Stéphane Cruveiller
- Laboratoire de Génomique Comparative, CNRS UMR8030, Institut de Génomique, CEA, Génoscope, Evry, France
| | - Antoine Danchin
- Unité de Génétique des Génomes Bactériens, Institut Pasteur, CNRS URA2171, Paris, France
| | - Médéric Diard
- Faculté de Médecine, Université Paris 5 René Descartes, INSERM U571, Paris, France
| | | | - Meriem El Karoui
- UR888 Unité des Bactéries Lactiques et Pathogènes Opportunistes, INRA, Jouy en Josas, France
| | - Eric Frapy
- Faculté de Médecine, Université Paris 5 René Descartes, INSERM U570, Paris, France
| | - Louis Garry
- Faculté de Médecine, Université Paris 7 Denis Diderot, INSERM U722, Site Xavier Bichat, Paris, France
| | - Jean Marc Ghigo
- Unité de Génétique des Biofilms, Institut Pasteur, CNRS URA2172, Paris, France
| | - Anne Marie Gilles
- Unité de Génétique des Génomes Bactériens, Institut Pasteur, CNRS URA2171, Paris, France
| | - James Johnson
- Veterans Affairs Medical Center, Minneapolis, Minnesota, United States of America
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota, United States of America
| | | | - Mathilde Lescat
- Faculté de Médecine, Université Paris 7 Denis Diderot, INSERM U722, Site Xavier Bichat, Paris, France
| | | | | | - Ivan Matic
- Faculté de Médecine, Université Paris 5 René Descartes, INSERM U571, Paris, France
| | - Xavier Nassif
- Faculté de Médecine, Université Paris 5 René Descartes, INSERM U570, Paris, France
| | - Sophie Oztas
- Génoscope, Institut de Génomique, CEA, Evry, France
| | - Marie Agnès Petit
- UR888 Unité des Bactéries Lactiques et Pathogènes Opportunistes, INRA, Jouy en Josas, France
| | - Christophe Pichon
- Pathogénie Bactérienne des Muqueuses, Institut Pasteur, Paris, France
| | - Zoé Rouy
- Laboratoire de Génomique Comparative, CNRS UMR8030, Institut de Génomique, CEA, Génoscope, Evry, France
| | - Claude Saint Ruf
- Faculté de Médecine, Université Paris 5 René Descartes, INSERM U571, Paris, France
| | | | - Jérôme Tourret
- Faculté de Médecine, Université Paris 7 Denis Diderot, INSERM U722, Site Xavier Bichat, Paris, France
| | | | - David Vallenet
- Laboratoire de Génomique Comparative, CNRS UMR8030, Institut de Génomique, CEA, Génoscope, Evry, France
| | - Claudine Médigue
- Laboratoire de Génomique Comparative, CNRS UMR8030, Institut de Génomique, CEA, Génoscope, Evry, France
- * E-mail: (CM); (EPCR); (ED)
| | - Eduardo P. C. Rocha
- Atelier de BioInformatique, Université Pierre et Marie Curie - Paris 6 (UPMC), Paris, France
- Microbial Evolutionary Genomics, Institut Pasteur, CNRS URA2171, Paris, France
- * E-mail: (CM); (EPCR); (ED)
| | - Erick Denamur
- Faculté de Médecine, Université Paris 7 Denis Diderot, INSERM U722, Site Xavier Bichat, Paris, France
- * E-mail: (CM); (EPCR); (ED)
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Abstract
In recent years, the importance of horizontal gene transfer (HGT) in bacterial evolution has been elevated to such a degree that many bacteriologists now question the very existence of bacterial species. If gene transfer is as rampant as comparative genomic studies have suggested, how could bacterial species survive such genomic fluidity? And yet, most bacteriologists recognize, and name, as species, clusters of bacterial isolates that share complex phenotypic properties. The Core Genome Hypothesis (CGH) has been proposed to explain this apparent paradox of fluid bacterial genomes associated with stable phenotypic clusters. It posits that there is a core of genes responsible for maintaining the species-specific phenotypic clusters observed throughout bacterial diversity and argues that, even in the face of substantial genomic fluidity, bacterial species can be rationally identified and named.
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Affiliation(s)
- Margaret A Riley
- Department of Biology, University of Massachusetts, Amherst, MA, USA
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Orsi RH, Ripoll DR, Yeung M, Nightingale KK, Wiedmann M. Recombination and positive selection contribute to evolution of Listeria monocytogenes inlA. MICROBIOLOGY-SGM 2007; 153:2666-2678. [PMID: 17660431 DOI: 10.1099/mic.0.2007/007310-0] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The surface molecule InlA interacts with E-cadherin to promote invasion of Listeria monocytogenes into selected host cells. DNA sequencing of inlA for 40 L. monocytogenes isolates revealed 107 synonymous and 45 nonsynonymous substitutions. A frameshift mutation in a homopolymeric tract encoding part of the InlA signal peptide was identified in three lineage II isolates, which also showed reduced ability to invade human intestinal epithelial cells. Phylogenies showed clear separation of inlA sequences into lineages I and II. Thirteen inlA recombination events, predominantly involving lineage II strains as recipients (12 events), were detected and a number of amino acid residues were shown to be under positive selection. Four of the 45 non-synonymous changes were found to be under positive selection with posterior probabilities >95 %. Mapping of polymorphic and positively selected amino acid sites on the partial crystal structure for InlA showed that the internalin surface of the leucine-rich repeat (LRR) region that faces the InlA receptor E-cadherin does not include any polymorphic sites; all polymorphic and positively selected amino acids mapped to the outer face of the LRR region or to other InlA regions. The data show that (i) inlA is highly polymorphic and evolution of inlA involved a considerable number of recombination events in lineage II isolates; (ii) positive selection at specific amino acid sites appears to contribute to evolution of inlA, including fixation of recombinant events; and (iii) single-nucleotide deletions in a lineage II-specific 3' homopolymeric tract in inlA lead to complete loss of InlA or to production of truncated InlA, which conveys reduced invasiveness. In conclusion, inlA has a complex evolutionary history, which is consistent with L. monocytogenes' natural history as an environmental pathogen with broad host-range, including its adaptation to environments and hosts where different inlA alleles may provide a selective advantage or where inlA may not be required.
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Affiliation(s)
- R H Orsi
- Department of Food Science, Cornell University, Ithaca, NY, USA
| | - D R Ripoll
- Computational Biology Service Unit, Cornell Theory Center, Cornell University, Ithaca, NY, USA
| | - M Yeung
- Department of Microbiology and Immunology, Cornell University, Ithaca, NY, USA
| | - K K Nightingale
- Department of Food Science, Cornell University, Ithaca, NY, USA
| | - M Wiedmann
- Department of Food Science, Cornell University, Ithaca, NY, USA
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Wildschutte H, Lawrence JG. Differential Salmonella survival against communities of intestinal amoebae. MICROBIOLOGY-SGM 2007; 153:1781-1789. [PMID: 17526835 DOI: 10.1099/mic.0.2006/003616-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Predation from intestinal amoebae may provide selective pressure for the maintenance of high genetic diversity at the Salmonella enterica rfb locus, whereby serovars better escape predators in particular environments depending on the O-antigens they express. Here, the hypothesis that amoebae from a particular intestinal environment collectively prefer one serovar over another is tested. Collections of Acanthamoeba, Tetramitus, Naegleria and Hartmannella were isolated from the intestinal tracts of several vertebrate hosts, including bullfrog tadpoles, goldfish, turtles and bearded dragons, and their feeding preferences were determined. Congeneric amoebae from the same environment had significantly similar feeding preferences. Strikingly, even unrelated amoebae - such as Naegleria and Tetramitus from goldfish - also had significantly similar feeding preferences. Yet amoebae isolated from different environments showed no similarity in prey choice. Thus, feeding preferences of amoebae appear to reflect their environment, not their taxonomic relationships. A mechanism mediating this phenotypic convergence is discussed.
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Affiliation(s)
- Hans Wildschutte
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15235, USA
| | - Jeffrey G Lawrence
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15235, USA
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38
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Abstract
Because bacterial recombination involves the occasional transfer of small DNA fragments between strains, different sets of niche-specific genes may be maintained in populations that freely recombine at other loci. Therefore, genetic isolation may be established at different times for different chromosomal regions during speciation as recombination at niche-specific genes is curtailed. To test this model, we separated sequence divergence into rate and time components, revealing that different regions of the Escherichia coli and Salmonella enterica chromosomes diverged over a approximately 70-million-year period. Genetic isolation first occurred at regions carrying species-specific genes, indicating that physiological distinctiveness between the nascent Escherichia and Salmonella lineages was maintained for tens of millions of years before the complete genetic isolation of their chromosomes.
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Affiliation(s)
- Adam C Retchless
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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Weissman SJ, Chattopadhyay S, Aprikian P, Obata-Yasuoka M, Yarova-Yarovaya Y, Stapleton A, Ba-Thein W, Dykhuizen D, Johnson JR, Sokurenko EV. Clonal analysis reveals high rate of structural mutations in fimbrial adhesins of extraintestinal pathogenic Escherichia coli. Mol Microbiol 2006; 59:975-88. [PMID: 16420365 PMCID: PMC1380272 DOI: 10.1111/j.1365-2958.2005.04985.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Type 1 fimbriae of Escherichia coli mediate mannose-specific adhesion to host epithelial surfaces and consist of a major, antigenically variable pilin subunit, FimA, and a minor, structurally conserved adhesive subunit, FimH, located on the fimbrial tip. We have analysed the variability of fimA and fimH in strains of vaginal and other origin that belong to one of the most prominent clonal groups of extraintestinal pathogenic E. coli, comprised of O1:K1-, O2:K1- and O18:K1-based serotypes. Multiple locus sequence typing (MLST) of this group revealed that the strains have identical (at all but one nucleotide position) eight housekeeping loci around the genome and belong to the ST95 complex defined by the publicly available E. coli MLST database. Multiple highly diverse fimA alleles have been introduced into the ST95 clonal complex via horizontal transfer, at a frequency comparable to that of genes defining the major O- and H-antigens. However, no further significant FimA diversification has occurred via point mutation after the transfers. In contrast, while fimH alleles also move horizontally (along with the fimA loci), they acquire point amino acid replacements at a higher rate than either housekeeping genes or fimA. These FimH mutations enhance binding to monomannose receptors and bacterial tropism for human vaginal epithelium. A similar pattern of rapid within-clonal structural evolution of the adhesive, but not pilin, subunit is also seen, respectively, in papG and papA alleles of the di-galactose-specific P-fimbriae. Thus, while structurally diverse pilin subunits of E. coli fimbriae are under selective pressure for frequent horizontal transfer between clones, the adhesive subunits of extraintestinal E. coli are under strong positive selection (Dn/Ds > 1 for fimH and papG) for functionally adaptive amino acid replacements.
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Affiliation(s)
- Scott J. Weissman
- Division of Infectious Disease, Immunology and Rheumatology, Department of Pediatrics, University of Washington, Seattle, WA, USA
| | | | - Pavel Aprikian
- Department of Microbiology, University of Washington, Seattle, WA, USA
| | - Mana Obata-Yasuoka
- Department of Obstetrics/Gynecology, University of Tsukuba, Tsukuba, Japan
| | - Yuliya Yarova-Yarovaya
- Division of Allergy and Infectious Disease, Department of Medicine, University of Washington, Seattle, WA, USA
| | - Ann Stapleton
- Division of Allergy and Infectious Disease, Department of Medicine, University of Washington, Seattle, WA, USA
| | - William Ba-Thein
- Department of Microbiology/Immunology, Thammasit University, Pathum-Thani, Thailand
| | - Daniel Dykhuizen
- Department of Evolutionary Biology, State University of New York, Stony Brook, NY, USA
| | - James R. Johnson
- Mucosal and Vaccine Research Center, Minneapolis VA Medical Center, University of Minnesota, Minneapolis, MN, USA
- Department of Medicine, University of Minnesota, Minneapolis, MN, USA
| | - Evgeni V. Sokurenko
- Department of Microbiology, University of Washington, Seattle, WA, USA
- *For correspondence. E-mail ; Tel. (+1) 206 685 2162; Fax (+1) 206 543 8297
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Tominaga A, Lan R, Reeves PR. Evolutionary changes of the flhDC flagellar master operon in Shigella strains. J Bacteriol 2005; 187:4295-302. [PMID: 15937193 PMCID: PMC1151726 DOI: 10.1128/jb.187.12.4295-4302.2005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Shigella strains are nonmotile. The master operon of flagellar synthesis, flhDC, was analyzed for genetic damage in 46 Shigella strains representing all known serotypes. In 11 strains (B1, B3, B6, B8, B10, B18, D5, F1B, D10, F3A, and F3C) the flhDC operon was completely deleted. PCR and sequence analysis of the flhDC region of the remaining 35 strains revealed many insertions or deletions associated with insertion sequences, and the majority of the strains were found to be defective in their flhDC genes. As these genes also play a role in regulation of non-flagellar genes, the loss may have other consequences or be driven by selection pressures other than those against flagellar motility. It has been suggested that Shigella strains fall mostly into three clusters within Escherichia coli, with five outlier strains, four of which are also within E. coli (G. M. Pupo, R. Lan, and P. R. Reeves, Proc. Natl. Acad. Sci. USA 97:10567-10572, 2000). The distribution of genetic changes in the flhDC region correlated very well with the three clusters and outlier strains found using housekeeping gene DNA sequences, enabling us to follow the sequence of mutational change in the flhDC locus. Two cluster 2 strains were found to have unique flhDC sequences, which are most probably due to recombination during the exchange of the adjacent O-antigen gene clusters.
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Affiliation(s)
- Akira Tominaga
- School of Molecular and Microbial Biosciences (GO8), The University of Sydney, Sydney, NSW 2006, Australia
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Gladitz J, Shen K, Antalis P, Hu FZ, Post JC, Ehrlich GD. Codon usage comparison of novel genes in clinical isolates of Haemophilus influenzae. Nucleic Acids Res 2005; 33:3644-58. [PMID: 15983137 PMCID: PMC1160521 DOI: 10.1093/nar/gki670] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A similarity statistic for codon usage was developed and used to compare novel gene sequences found in clinical isolates of Haemophilus influenzae with a reference set of 80 prokaryotic, eukaryotic and viral genomes. These analyses were performed to obtain an indication as to whether individual genes were Haemophilus-like in nature, or if they probably had more recently entered the H.influenzae gene pool via horizontal gene transfer from other species. The average and SD values were calculated for the similarity statistics from a study of the set of all genes in the H.influenzae Rd reference genome that encoded proteins of 100 amino acids or longer. Approximately 80% of Rd genes gave a statistic indicating that they were most like other Rd genes. Genes displaying codon usage statistics >1 SD above this range were either considered part of the highly expressed group of H.influenzae genes, or were considered of foreign origin. An alternative determinant for identifying genes of foreign origin was when the similarity statistics produced a value that was much closer to a non-H.influenzae reference organism than to any of the Haemophilus species contained in the reference set. Approximately 65% of the novel sequences identified in the H.influenzae clinical isolates displayed codon usages most similar to Haemophilus sp. The remaining novel sequences produced similarity statistics closer to one of the other reference genomes thereby suggesting that these sequences may have entered the H.influenzae gene pool more recently via horizontal transfer.
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Affiliation(s)
| | | | | | | | | | - Garth D. Ehrlich
- To whom correspondence should be addressed. Tel: +1 412 359 4228; Fax: +1 412 359 6995;
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