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Yamamoto S, Iyoda S, Ohnishi M. Stabilizing Genetically Unstable Simple Sequence Repeats in the Campylobacter jejuni Genome by Multiplex Genome Editing: a Reliable Approach for Delineating Multiple Phase-Variable Genes. mBio 2021; 12:e0140121. [PMID: 34425708 PMCID: PMC8437040 DOI: 10.1128/mbio.01401-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Accepted: 07/21/2021] [Indexed: 11/20/2022] Open
Abstract
Hypermutable simple sequence repeats (SSRs) are major drivers of phase variation in Campylobacter jejuni. The presence of multiple SSR-mediated phase-variable genes encoding enzymes that modify surface structures, including capsular polysaccharide (CPS) and lipooligosaccharide (LOS), generates extreme cell surface diversity within bacterial populations, thereby promoting adaptation to selective pressures in host environments. Therefore, genetically controlling SSR-mediated phase variation can be important for achieving stable and reproducible research on C. jejuni. Here, we show that natural "cotransformation" is an effective method for C. jejuni genome editing. Cotransformation is a trait of naturally competent bacteria that causes uptake/integration of multiple different DNA molecules, which has been recently adapted to multiplex genome editing by natural transformation (MuGENT), a method for introducing multiple mutations into the genomes of these bacteria. We found that cotransformation efficiently occurred in C. jejuni. To examine the feasibility of MuGENT in C. jejuni, we "locked" different polyG SSR tracts in strain NCTC11168 (which are located in the biosynthetic CPS/LOS gene clusters) into either the ON or OFF configurations. This approach, termed "MuGENT-SSR," enabled the generation of all eight edits within 2 weeks and the identification of a phase-locked strain with a highly stable type of Penner serotyping, a CPS-based serotyping scheme. Furthermore, extensive genome editing of this strain by MuGENT-SSR identified a phase-variable gene that determines the Penner serotype of NCTC11168. Thus, MuGENT-SSR provides a platform for genetic and phenotypic engineering of genetically unstable C. jejuni, making it a reliable approach for elucidating the mechanisms underlying phase-variable expression of specific phenotypes. IMPORTANCE Campylobacter jejuni is the leading bacterial cause of foodborne gastroenteritis in developed countries and occasionally progresses to the autoimmune disease Guillain-Barré syndrome. A relatively large number of hypermutable simple sequence repeat (SSR) tracts in the C. jejuni genome markedly decreases its phenotypic stability through reversible changes in the ON or OFF expression states of the genes in which they reside, a phenomenon called phase variation. Thus, controlling SSR-mediated phase variation can be important for achieving stable and reproducible research on C. jejuni. In this study, we developed a feasible and effective approach for genetically manipulate multiple SSR tracts in the C. jejuni genome using natural cotransformation, a trait of naturally transformable bacterial species that causes the uptake and integration of multiple different DNA molecules. This approach will greatly help to improve the genetic and phenotypic stability of C. jejuni to enable diverse applications in research and development.
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Affiliation(s)
- Shouji Yamamoto
- Department of Bacteriology I, National Institute of Infectious Diseases, Tokyo, Japan
| | - Sunao Iyoda
- Department of Bacteriology I, National Institute of Infectious Diseases, Tokyo, Japan
| | - Makoto Ohnishi
- Department of Bacteriology I, National Institute of Infectious Diseases, Tokyo, Japan
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Wanford JJ, Lango-Scholey L, Nothaft H, Hu Y, Szymanski CM, Bayliss CD. Random sorting of Campylobacter jejuni phase variants due to a narrow bottleneck during colonization of broiler chickens. MICROBIOLOGY-SGM 2019; 164:896-907. [PMID: 29856309 PMCID: PMC6097035 DOI: 10.1099/mic.0.000669] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Phase variation (PV), involving stochastic switches in gene expression, is exploited by the human pathogen Campylobacter jejuni to adapt to different environmental and host niches. Phase-variable genes of C. jejuni modulate expression of multiple surface determinants, and hence may influence host colonization. Population bottlenecks can rapidly remove the diversity generated by PV, and strict single-cell bottlenecks can lead to propagation of PV states with highly divergent phenotypes. Using a combination of high-throughput fragment size analysis and comparison with in vivo and in silico bottleneck models, we have characterized a narrow population bottleneck during the experimental colonization of broiler chickens with C. jejuni strain 81-176. We identified high levels of variation in five PV genes in the inoculum, and subsequently, massively decreased population diversity following colonization. Each bird contained a dominant five-gene phasotype that was present in the inoculum indicative of random sorting through a narrow, non-selective bottleneck during colonization. These results are evidence of the potential for confounding effects of PV on in vivo studies of Campylobacter colonization factors and poultry vaccine studies. Our results are also an argument for population bottlenecks as mediators of stochastic variability in the propensity to survive through the food chain and cause clinical human disease.
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Affiliation(s)
- Joseph J Wanford
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
| | - Lea Lango-Scholey
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
| | - Harald Nothaft
- Department of Biological Sciences, University of Alberta, Edmonton, Canada
| | - Yue Hu
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
| | - Christine M Szymanski
- Department of Microbiology and Complex Carbohydrate Research Center, University of Georgia, Athens, USA.,Department of Biological Sciences, University of Alberta, Edmonton, Canada
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Liang SH, Anderson MZ, Hirakawa MP, Wang JM, Frazer C, Alaalm LM, Thomson GJ, Ene IV, Bennett RJ. Hemizygosity Enables a Mutational Transition Governing Fungal Virulence and Commensalism. Cell Host Microbe 2019; 25:418-431.e6. [PMID: 30824263 DOI: 10.1016/j.chom.2019.01.005] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2018] [Revised: 10/03/2018] [Accepted: 01/14/2019] [Indexed: 12/21/2022]
Abstract
Candida albicans is a commensal fungus of human gastrointestinal and reproductive tracts, but also causes life-threatening systemic infections. The balance between colonization and pathogenesis is associated with phenotypic plasticity, with alternative cell states producing different outcomes in a mammalian host. Here, we reveal that gene dosage of a master transcription factor regulates cell differentiation in diploid C. albicans cells, as EFG1 hemizygous cells undergo a phenotypic transition inaccessible to "wild-type" cells with two functional EFG1 alleles. Notably, clinical isolates are often EFG1 hemizygous and thus licensed to undergo this transition. Phenotypic change corresponds to high-frequency loss of the functional EFG1 allele via de novo mutation or gene conversion events. This phenomenon also occurs during passaging in the gastrointestinal tract with the resulting cell type being hypercompetitive for commensal and systemic infections. A "two-hit" genetic model therefore underlies a key phenotypic transition in C. albicans that enables adaptation to host niches.
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Affiliation(s)
- Shen-Huan Liang
- Molecular Microbiology and Immunology Department, Brown University, Providence, RI 02912, USA
| | - Matthew Z Anderson
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA; Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH 43210, USA
| | - Matthew P Hirakawa
- Molecular Microbiology and Immunology Department, Brown University, Providence, RI 02912, USA
| | - Joshua M Wang
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA; Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH 43210, USA
| | - Corey Frazer
- Molecular Microbiology and Immunology Department, Brown University, Providence, RI 02912, USA
| | - Leenah M Alaalm
- Molecular Microbiology and Immunology Department, Brown University, Providence, RI 02912, USA
| | - Gregory J Thomson
- Molecular Microbiology and Immunology Department, Brown University, Providence, RI 02912, USA
| | - Iuliana V Ene
- Molecular Microbiology and Immunology Department, Brown University, Providence, RI 02912, USA
| | - Richard J Bennett
- Molecular Microbiology and Immunology Department, Brown University, Providence, RI 02912, USA.
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4
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Wanford JJ, Green LR, Aidley J, Bayliss CD. Phasome analysis of pathogenic and commensal Neisseria species expands the known repertoire of phase variable genes, and highlights common adaptive strategies. PLoS One 2018; 13:e0196675. [PMID: 29763438 PMCID: PMC5953494 DOI: 10.1371/journal.pone.0196675] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Accepted: 04/17/2018] [Indexed: 12/02/2022] Open
Abstract
Pathogenic Neisseria are responsible for significantly higher levels of morbidity and mortality than their commensal relatives despite having similar genetic contents. Neisseria possess a disparate arsenal of surface determinants that facilitate host colonisation and evasion of the immune response during persistent carriage. Adaptation to rapid changes in these hostile host environments is enabled by phase variation (PV) involving high frequency, stochastic switches in expression of surface determinants. In this study, we analysed 89 complete and 79 partial genomes, from the NCBI and Neisseria PubMLST databases, representative of multiple pathogenic and commensal species of Neisseria using PhasomeIt, a new program that identifies putatively phase-variable genes and homology groups by the presence of simple sequence repeats (SSR). We detected a repertoire of 884 putative PV loci with maxima of 54 and 47 per genome in gonococcal and meningococcal isolates, respectively. Most commensal species encoded a lower number of PV genes (between 5 and 30) except N. lactamica wherein the potential for PV (36–82 loci) was higher, implying that PV is an adaptive mechanism for persistence in this species. We also characterised the repeat types and numbers in both pathogenic and commensal species. Conservation of SSR-mediated PV was frequently observed in outer membrane proteins or modifiers of outer membrane determinants. Intermittent and weak selection for evolution of SSR-mediated PV was suggested by poor conservation of tracts with novel PV genes often occurring in only one isolate. Finally, we describe core phasomes—the conserved repertoires of phase-variable genes—for each species that identify overlapping but distinctive adaptive strategies for the pathogenic and commensal members of the Neisseria genus.
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Affiliation(s)
- Joseph J. Wanford
- Department of Genetics and Genome Biology, University of Leicester, Leicestershire, United Kingdom
- * E-mail:
| | - Luke R. Green
- Department of Genetics and Genome Biology, University of Leicester, Leicestershire, United Kingdom
| | - Jack Aidley
- Department of Genetics and Genome Biology, University of Leicester, Leicestershire, United Kingdom
| | - Christopher D. Bayliss
- Department of Genetics and Genome Biology, University of Leicester, Leicestershire, United Kingdom
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Moxon R, Kussell E. The impact of bottlenecks on microbial survival, adaptation, and phenotypic switching in host-pathogen interactions. Evolution 2017; 71:2803-2816. [PMID: 28983912 DOI: 10.1111/evo.13370] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2017] [Accepted: 09/01/2017] [Indexed: 12/18/2022]
Abstract
Microbial pathogens and viruses can often maintain sufficient population diversity to evade a wide range of host immune responses. However, when populations experience bottlenecks, as occurs frequently during initiation of new infections, pathogens require specialized mechanisms to regenerate diversity. We address the evolution of such mechanisms, known as stochastic phenotype switches, which are prevalent in pathogenic bacteria. We analyze a model of pathogen diversification in a changing host environment that accounts for selective bottlenecks, wherein different phenotypes have distinct transmission probabilities between hosts. We show that under stringent bottlenecks, such that only one phenotype can initiate new infections, there exists a threshold stochastic switching rate below which all pathogen lineages go extinct, and above which survival is a near certainty. We determine how quickly stochastic switching rates can evolve by computing a fitness landscape for the evolutionary dynamics of switching rates, and analyzing its dependence on both the stringency of bottlenecks and the duration of within-host growth periods. We show that increasing the stringency of bottlenecks or decreasing the period of growth results in faster adaptation of switching rates. Our model provides strong theoretical evidence that bottlenecks play a critical role in accelerating the evolutionary dynamics of pathogens.
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Affiliation(s)
- Richard Moxon
- University of Oxford Medical Sciences Division, John Radcliffe Hospital, Oxford, United Kingdom
| | - Edo Kussell
- Department of Biology and Center for Genomics and Systems Biology, 12 Waverly Place, New York University, New York, 10003.,Department of Physics, New York University, 726 Broadway, New York, 10003
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Phase and antigenic variation govern competition dynamics through positioning in bacterial colonies. Sci Rep 2017; 7:12151. [PMID: 28939833 PMCID: PMC5610331 DOI: 10.1038/s41598-017-12472-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 09/11/2017] [Indexed: 01/07/2023] Open
Abstract
Cellular positioning towards the surface of bacterial colonies and biofilms can enhance dispersal, provide a selective advantage due to increased nutrient and space availability, or shield interior cells from external stresses. Little is known about the molecular mechanisms that govern bacterial positioning. Using the type IV pilus (T4P) of Neisseria gonorrhoeae, we tested the hypothesis that the processes of phase and antigenic variation govern positioning and thus enhance bacterial fitness in expanding gonococcal colonies. By independently tuning growth rate and T4P-mediated interaction forces, we show that the loss of T4P and the subsequent segregation to the front confers a strong selective advantage. Sequencing of the major pilin gene of the spatially segregated sub-populations and an investigation of the spatio-temporal population dynamics was carried out. Our findings indicate that pilin phase and antigenic variation generate a standing variation of pilin sequences within the inoculation zone, while variants associated with a non-piliated phenotype segregate to the front of the growing colony. We conclude that tuning of attractive forces by phase and antigenic variation is a powerful mechanism for governing the dynamics of bacterial colonies.
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Suárez-Esquivel M, Ruiz-Villalobos N, Castillo-Zeledón A, Jiménez-Rojas C, Roop Ii RM, Comerci DJ, Barquero-Calvo E, Chacón-Díaz C, Caswell CC, Baker KS, Chaves-Olarte E, Thomson NR, Moreno E, Letesson JJ, De Bolle X, Guzmán-Verri C. Brucella abortus Strain 2308 Wisconsin Genome: Importance of the Definition of Reference Strains. Front Microbiol 2016; 7:1557. [PMID: 27746773 PMCID: PMC5041503 DOI: 10.3389/fmicb.2016.01557] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Accepted: 09/16/2016] [Indexed: 12/25/2022] Open
Abstract
Brucellosis is a bacterial infectious disease affecting a wide range of mammals and a neglected zoonosis caused by species of the genetically homogenous genus Brucella. As in most studies on bacterial diseases, research in brucellosis is carried out by using reference strains as canonical models to understand the mechanisms underlying host pathogen interactions. We performed whole genome sequencing analysis of the reference strain B. abortus 2308 routinely used in our laboratory, including manual curated annotation accessible as an editable version through a link at https://en.wikipedia.org/wiki/Brucella#Genomics. Comparison of this genome with two publically available 2308 genomes showed significant differences, particularly indels related to insertional elements, suggesting variability related to the transposition of these elements within the same strain. Considering the outcome of high resolution genomic techniques in the bacteriology field, the conventional concept of strain definition needs to be revised.
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Affiliation(s)
- Marcela Suárez-Esquivel
- Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional de Costa Rica Heredia, Costa Rica
| | - Nazareth Ruiz-Villalobos
- Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional de Costa Rica Heredia, Costa Rica
| | - Amanda Castillo-Zeledón
- Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional de Costa Rica Heredia, Costa Rica
| | - César Jiménez-Rojas
- Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional de Costa Rica Heredia, Costa Rica
| | - R Martin Roop Ii
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University Greenville, NC, USA
| | - Diego J Comerci
- Instituto de Investigaciones Biotecnológicas "Dr. Rodolfo A. Ugalde", Instituto Tecnológico de Chascomús, Universidad Nacional de San Martín, Consejo Nacional de Investigaciones Científicas y Técnicas, Comisión Nacional de Energía Atómica, Grupo Pecuario, Centro Atómico Ezeiza Buenos Aires, Argentina
| | - Elías Barquero-Calvo
- Centro de Investigación en Enfermedades Tropicales, Facultad de Microbiología, Universidad de Costa Rica San José, Costa Rica
| | - Carlos Chacón-Díaz
- Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional de Costa RicaHeredia, Costa Rica; Centro de Investigación en Enfermedades Tropicales, Facultad de Microbiología, Universidad de Costa RicaSan José, Costa Rica
| | - Clayton C Caswell
- Center for Molecular Medicine and Infectious Diseases, Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech Blacksburg, VA, USA
| | - Kate S Baker
- Wellcome Trust Sanger InstituteHinxton, UK; Department of Functional and Comparative Genomics, Institute of Integrative Biology, University of LiverpoolLiverpool, UK
| | - Esteban Chaves-Olarte
- Centro de Investigación en Enfermedades Tropicales, Facultad de Microbiología, Universidad de Costa Rica San José, Costa Rica
| | - Nicholas R Thomson
- Wellcome Trust Sanger InstituteHinxton, UK; The London School of Hygiene and Tropical MedicineLondon, UK
| | - Edgardo Moreno
- Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional de Costa RicaHeredia, Costa Rica; Instituto Clodomiro Picado, Universidad de Costa RicaSan José, Costa Rica
| | - Jean J Letesson
- Unité de Recherche en Biologie des Microorganismes, Université de Namur Namur Belgium
| | - Xavier De Bolle
- Unité de Recherche en Biologie des Microorganismes, Université de Namur Namur Belgium
| | - Caterina Guzmán-Verri
- Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional de Costa RicaHeredia, Costa Rica; Centro de Investigación en Enfermedades Tropicales, Facultad de Microbiología, Universidad de Costa RicaSan José, Costa Rica
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Lango-Scholey L, Aidley J, Woodacre A, Jones MA, Bayliss CD. High Throughput Method for Analysis of Repeat Number for 28 Phase Variable Loci of Campylobacter jejuni Strain NCTC11168. PLoS One 2016; 11:e0159634. [PMID: 27466808 PMCID: PMC4965091 DOI: 10.1371/journal.pone.0159634] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 07/05/2016] [Indexed: 11/19/2022] Open
Abstract
Mutations in simple sequence repeat tracts are a major mechanism of phase variation in several bacterial species including Campylobacter jejuni. Changes in repeat number of tracts located within the reading frame can produce a high frequency of reversible switches in gene expression between ON and OFF states. The genome of C. jejuni strain NCTC11168 contains 29 loci with polyG/polyC tracts of seven or more repeats. This protocol outlines a method—the 28-locus-CJ11168 PV-analysis assay—for rapidly determining ON/OFF states of 28 of these phase-variable loci in a large number of individual colonies from C. jejuni strain NCTC11168. The method combines a series of multiplex PCR assays with a fragment analysis assay and automated extraction of fragment length, repeat number and expression state. This high throughput, multiplex assay has utility for detecting shifts in phase variation states within and between populations over time and for exploring the effects of phase variation on adaptation to differing selective pressures. Application of this method to analysis of the 28 polyG/polyC tracts in 90 C. jejuni colonies detected a 2.5-fold increase in slippage products as tracts lengthened from G8 to G11 but no difference between tracts of similar length indicating that flanking sequence does not influence slippage rates. Comparison of this observed slippage to previously measured mutation rates for G8 and G11 tracts in C. jejuni indicates that PCR amplification of a DNA sample will over-estimate phase variation frequencies by 20-35-fold. An important output of the 28-locus-CJ11168 PV-analysis assay is combinatorial expression states that cannot be determined by other methods. This method can be adapted to analysis of phase variation in other C. jejuni strains and in a diverse range of bacterial species.
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Affiliation(s)
- Lea Lango-Scholey
- School for Veterinary Medicine, University of Nottingham, Nottingham, United Kingdom
| | - Jack Aidley
- Department of Genetics, University of Leicester, Leicester, United Kingdom
| | - Alexandra Woodacre
- Department of Genetics, University of Leicester, Leicester, United Kingdom
| | - Michael A. Jones
- School for Veterinary Medicine, University of Nottingham, Nottingham, United Kingdom
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Bakour S, Sankar SA, Rathored J, Biagini P, Raoult D, Fournier PE. Identification of virulence factors and antibiotic resistance markers using bacterial genomics. Future Microbiol 2016; 11:455-66. [PMID: 26974504 DOI: 10.2217/fmb.15.149] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
In recent years, the number of multidrug-resistant bacteria has increased rapidly and several epidemics were signaled in different regions of the world. Faced with this situation that presents a major global public health concern, the development and the use of new and rapid technologies is more than urgent. The use of the next-generation sequencing platforms by microbiologists and infectious disease specialists has allowed great progress in the medical field. Here, we review the usefulness of whole-genome sequencing for the detection of virulence and antibiotic resistance associated genes.
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Affiliation(s)
- Sofiane Bakour
- Unité de recherche sur les maladies infectieuses et tropicales émergentes (URMITE), UM 63, CNRS 7278, IRD 198, INSERM 1095, IHU Méditerranée Infection, Faculté de Médecine et de Pharmacie, Aix-Marseille-Université, Marseille, France
| | - Senthil Alias Sankar
- Unité de recherche sur les maladies infectieuses et tropicales émergentes (URMITE), UM 63, CNRS 7278, IRD 198, INSERM 1095, IHU Méditerranée Infection, Faculté de Médecine et de Pharmacie, Aix-Marseille-Université, Marseille, France
| | - Jaishriram Rathored
- Unité de recherche sur les maladies infectieuses et tropicales émergentes (URMITE), UM 63, CNRS 7278, IRD 198, INSERM 1095, IHU Méditerranée Infection, Faculté de Médecine et de Pharmacie, Aix-Marseille-Université, Marseille, France
| | - Philippe Biagini
- UMR CNRS 7268 Equipe "Emergence et coévolution virale," Etablissement Français du Sang Alpes-Méditerranée et Aix-Marseille Université, 27 Boulevard Jean Moulin, 13005 Marseille
| | - Didier Raoult
- Unité de recherche sur les maladies infectieuses et tropicales émergentes (URMITE), UM 63, CNRS 7278, IRD 198, INSERM 1095, IHU Méditerranée Infection, Faculté de Médecine et de Pharmacie, Aix-Marseille-Université, Marseille, France
| | - Pierre-Edouard Fournier
- Unité de recherche sur les maladies infectieuses et tropicales émergentes (URMITE), UM 63, CNRS 7278, IRD 198, INSERM 1095, IHU Méditerranée Infection, Faculté de Médecine et de Pharmacie, Aix-Marseille-Université, Marseille, France
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10
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Saeed AF, Wang R, Wang S. Microsatellites in Pursuit of Microbial Genome Evolution. Front Microbiol 2016; 6:1462. [PMID: 26779133 PMCID: PMC4700210 DOI: 10.3389/fmicb.2015.01462] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2015] [Accepted: 12/07/2015] [Indexed: 12/27/2022] Open
Abstract
Microsatellites or short sequence repeats are widespread genetic markers which are hypermutable 1-6 bp long short nucleotide motifs. Significantly, their applications in genetics are extensive due to their ceaseless mutational degree, widespread length variations and hypermutability skills. These features make them useful in determining the driving forces of evolution by using powerful molecular techniques. Consequently, revealing important questions, for example, what is the significance of these abundant sequences in DNA, what are their roles in genomic evolution? The answers of these important questions are hidden in the ways these short motifs contributed in altering the microbial genomes since the origin of life. Even though their size ranges from 1 -to- 6 bases, these repeats are becoming one of the most popular genetic probes in determining their associations and phylogenetic relationships in closely related genomes. Currently, they have been widely used in molecular genetics, biotechnology and evolutionary biology. However, due to limited knowledge; there is a significant gap in research and lack of information concerning hypermutational mechanisms. These mechanisms play a key role in microsatellite loci point mutations and phase variations. This review will extend the understandings of impacts and contributions of microsatellite in genomic evolution and their universal applications in microbiology.
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Affiliation(s)
- Abdullah F. Saeed
- Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry UniversityFuzhou, China
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11
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Phase variation mediates reductions in expression of surface proteins during persistent meningococcal carriage. Infect Immun 2014; 82:2472-84. [PMID: 24686058 DOI: 10.1128/iai.01521-14] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Asymptomatic and persistent colonization of the upper respiratory tract by Neisseria meningitidis occurs despite elicitation of adaptive immune responses against surface antigens. A putative mechanism for facilitating host persistence of this bacterial commensal and pathogen is alterations in expression of surface antigens by simple sequence repeat (SSR)-mediated phase variation. We investigated how often phase variation occurs during persistent carriage by analyzing the SSRs of eight loci in multiple isolates from 21 carriers representative of 1 to 6 months carriage. Alterations in repeat number were detected by a GeneScan analysis and occurred at 0.06 mutations/gene/month of carriage. The expression states were determined by Western blotting and two genes, fetA and nadA, exhibited trends toward low expression states. A critical finding from our unique examination of combinatorial expression states, "phasotypes," was for significant reductions in expression of multiple phase-variable surface proteins during persistent carriage of some strains. The immune responses in these carriers were examined by measuring variant-specific PorA IgG antibodies, capsular group Y IgG antibodies and serum bactericidal activity in concomitant serum samples. Persistent carriage was associated with high levels of specific IgG antibodies and serum bactericidal activity while recent strain acquisition correlated with a significant induction of antibodies. We conclude that phase-variable genes are driven into lower expression states during long-term persistent meningococcal carriage, in part due to continuous exposure to antibody-mediated selection, suggesting localized hypermutation has evolved to facilitate host persistence.
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