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Comparative genomics reveals genus specific encoding of amino acids by tri-nucleotide SSRs in human pathogenic Streptococcus and Staphylococcus bacteria. Biologia (Bratisl) 2022. [DOI: 10.1007/s11756-022-01143-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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2
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Mukherjee A, Dechow-Seligmann G, Gallie J. Evolutionary flexibility in routes to mat formation by Pseudomonas. Mol Microbiol 2021; 117:394-410. [PMID: 34856020 DOI: 10.1111/mmi.14855] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 11/30/2021] [Accepted: 11/30/2021] [Indexed: 11/27/2022]
Abstract
Many bacteria form mats at the air-liquid interface of static microcosms. These structures typically involve the secretion of exopolysaccharides, the production of which is often controlled by the secondary messenger c-di-GMP. Mechanisms of mat formation have been particularly well characterized in Pseudomonas fluorescens SBW25; stimuli or mutations that increase c-di-GMP production by diguanylate cyclases (WspR, AwsR, and MwsR) result in the secretion of cellulose and mat formation. Here, we characterize and compare mat formation in two close relatives of SBW25: Pseudomonas simiae PICF7 and P. fluorescens A506. We find that PICF7-the strain more closely related to SBW25-can form mats through mutations affecting the activity of the same three diguanylate cyclases as SBW25. However, instead of cellulose, these mutations activate production of the exopolysaccharide Pel. We also provide evidence for at least two further-as yet uncharacterized-routes to mat formation by PICF7. P. fluorescens A506, while retaining the same mutational routes to mat formation as SBW25 and PICF7, preferentially forms mats by a semi-heritable mechanism that culminates in Psl and Pga over-production. Our results demonstrate a high level of evolutionary flexibility in the molecular and structural routes to mat formation, even among close relatives.
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Affiliation(s)
- Anuradha Mukherjee
- Department of Evolutionary Theory, Max Planck Institute for Evolutionary Biology, Plön, Germany
| | - Gunda Dechow-Seligmann
- Department of Evolutionary Theory, Max Planck Institute for Evolutionary Biology, Plön, Germany
| | - Jenna Gallie
- Department of Evolutionary Theory, Max Planck Institute for Evolutionary Biology, Plön, Germany
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3
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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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4
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Dimitriu T, Szczelkun MD, Westra ER. Evolutionary Ecology and Interplay of Prokaryotic Innate and Adaptive Immune Systems. Curr Biol 2021; 30:R1189-R1202. [PMID: 33022264 DOI: 10.1016/j.cub.2020.08.028] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Like many organisms, bacteria and archaea have both innate and adaptive immune systems to defend against infection by viruses and other parasites. Innate immunity most commonly relies on the endonuclease-mediated cleavage of any incoming DNA that lacks a specific epigenetic modification, through a system known as restriction-modification. CRISPR-Cas-mediated adaptive immunity relies on the insertion of short DNA sequences from parasite genomes into CRISPR arrays on the host genome to provide sequence-specific protection. The discovery of each of these systems has revolutionised our ability to carry out genetic manipulations, and, as a consequence, the enzymes involved have been characterised in exquisite detail. In comparison, much less is known about the importance of these two arms of the defence for the ecology and evolution of prokaryotes and their parasites. Here, we review our current ecological and evolutionary understanding of these systems in isolation, and discuss the need to study how innate and adaptive immune responses are integrated when they coexist in the same cell.
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Affiliation(s)
- Tatiana Dimitriu
- Environment and Sustainability Institute, Biosciences, University of Exeter, Penryn TR10 9FE, UK.
| | - Mark D Szczelkun
- DNA-Protein Interactions Unit, School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK.
| | - Edze R Westra
- Environment and Sustainability Institute, Biosciences, University of Exeter, Penryn TR10 9FE, UK.
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5
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Payelleville A, Brillard J. Novel Identification of Bacterial Epigenetic Regulations Would Benefit From a Better Exploitation of Methylomic Data. Front Microbiol 2021; 12:685670. [PMID: 34054792 PMCID: PMC8160106 DOI: 10.3389/fmicb.2021.685670] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 04/22/2021] [Indexed: 12/21/2022] Open
Abstract
DNA methylation can be part of epigenetic mechanisms, leading to cellular subpopulations with heterogeneous phenotypes. While prokaryotic phenotypic heterogeneity is of critical importance for a successful infection by several major pathogens, the exact mechanisms involved in this phenomenon remain unknown in many cases. Powerful sequencing tools have been developed to allow the detection of the DNA methylated bases at the genome level, and they have recently been extensively applied on numerous bacterial species. Some of these tools are increasingly used for metagenomics analysis but only a limited amount of the available methylomic data is currently being exploited. Because newly developed tools now allow the detection of subpopulations differing in their genome methylation patterns, it is time to emphasize future strategies based on a more extensive use of methylomic data. This will ultimately help to discover new epigenetic gene regulations involved in bacterial phenotypic heterogeneity, including during host-pathogen interactions.
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Affiliation(s)
- Amaury Payelleville
- DGIMI, INRAE, Univ. Montpellier, Montpellier, France.,Cellular and Molecular Microbiology, Faculté des Sciences, Université Libre de Bruxelles, Gosselies, Belgium
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6
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Gor V, Ohniwa RL, Morikawa K. No Change, No Life? What We Know about Phase Variation in Staphylococcus aureus. Microorganisms 2021; 9:microorganisms9020244. [PMID: 33503998 PMCID: PMC7911514 DOI: 10.3390/microorganisms9020244] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 01/22/2021] [Accepted: 01/23/2021] [Indexed: 12/13/2022] Open
Abstract
Phase variation (PV) is a well-known phenomenon of high-frequency reversible gene-expression switching. PV arises from genetic and epigenetic mechanisms and confers a range of benefits to bacteria, constituting both an innate immune strategy to infection from bacteriophages as well as an adaptation strategy within an infected host. PV has been well-characterized in numerous bacterial species; however, there is limited direct evidence of PV in the human opportunistic pathogen Staphylococcus aureus. This review provides an overview of the mechanisms that generate PV and focuses on earlier and recent findings of PV in S. aureus, with a brief look at the future of the field.
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Affiliation(s)
- Vishal Gor
- Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
- Correspondence: (V.G.); (K.M.)
| | - Ryosuke L. Ohniwa
- Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan;
| | - Kazuya Morikawa
- Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan;
- Correspondence: (V.G.); (K.M.)
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7
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Moraxella catarrhalis phase-variable loci show differences in expression during conditions relevant to disease. PLoS One 2020; 15:e0234306. [PMID: 32555615 PMCID: PMC7302503 DOI: 10.1371/journal.pone.0234306] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Accepted: 05/22/2020] [Indexed: 11/29/2022] Open
Abstract
Moraxella catarrhalis is a human-adapted, opportunistic bacterial pathogen of the respiratory mucosa. Although asymptomatic colonization of the nasopharynx is common, M. catarrhalis can ascend into the middle ear, where it is a prevalent causative agent of otitis media in children, or enter the lower respiratory tract, where it is associated with acute exacerbations of chronic obstructive pulmonary disease in adults. Phase variation is the high frequency, random, reversible switching of gene expression that allows bacteria to adapt to different host microenvironments and evade host defences, and is most commonly mediated by simple DNA sequence repeats. Bioinformatic analysis of five closed M. catarrhalis genomes identified 17 unique simple DNA sequence repeat tracts that were variable between strains, indicating the potential to mediate phase variable expression of the associated genes. Assays designed to assess simple sequence repeat variation under conditions mimicking host infection demonstrated that phase variation of uspA1 (ubiquitous surface protein A1) from high to low expression occurs over 72 hours of biofilm passage, while phase variation of uspA2 (ubiquitous surface protein A2) to high expression variants occurs during repeated exposure to human serum, as measured by mRNA levels. We also identify and confirm the variable expression of two novel phase variable genes encoding a Type III DNA methyltransferase (modO), and a conserved hypothetical permease (MC25239_RS00020). These data reveal the repertoire of phase variable genes mediated by simple sequence repeats in M. catarrhalis and demonstrate that modulation of expression under conditions mimicking human infection is attributed to changes in simple sequence repeat length.
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8
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Wanford JJ, Holmes JC, Bayliss CD, Green LR. Meningococcal core and accessory phasomes vary by clonal complex. Microb Genom 2020; 6:e000367. [PMID: 32375989 PMCID: PMC7371114 DOI: 10.1099/mgen.0.000367] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 03/27/2020] [Indexed: 11/21/2022] Open
Abstract
Neisseria meningitidis is a Gram-negative human commensal pathogen, with extensive phenotypic plasticity afforded by phase-variable (PV) gene expression. Phase variation is a stochastic switch in gene expression from an ON to an OFF state, mediated by localized hypermutation of simple sequence repeats (SSRs). Circulating N. meningitidis clones vary in propensity to cause disease, with some clonal complexes (ccs) classified as hypervirulent and others as carriage-associated. We examined the PV gene repertoires, or phasome, of these lineages in order to determine whether phase variation contributes to disease propensity. We analysed 3328 genomes representative of nine circulating meningococcal ccs with PhasomeIt, a tool that identifies PV genes by the presence of SSRs and homologous gene clusters. The presence, absence and functions of all identified PV gene clusters were confirmed by annotation or blast searches within the Neisseria PubMLST database. While no significant differences were detected in the number of PV genes or the core, conserved phasome content between hypervirulent and carriage lineages, individual ccs exhibited major variations in PV gene numbers. Phylogenetic clusters produced by phasome or core genome analyses were similar, indicating co-evolution of PV genes with the core genome. While conservation of PV clusters is high, with 76 % present in all meningococcal isolates, maintenance of an SSR is variable, ranging from conserved in all isolates to present only in a single cc, indicating differing evolutionary trajectories for each lineage. Diverse functional groups of PV genes were present across the meningococcal lineages; however, the majority directly or indirectly influence bacterial surface antigens and could impact on future vaccine development. Finally, we observe that meningococci have open pan phasomes, indicating ongoing evolution of PV gene content and a significant potential for adaptive changes in this clinically relevant genus.
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Affiliation(s)
- Joseph J. Wanford
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
| | - Jonathan C. Holmes
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
| | | | - Luke R. Green
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, UK
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Harhay GP, Harhay DM, Bono JL, Capik SF, DeDonder KD, Apley MD, Lubbers BV, White BJ, Larson RL, Smith TPL. A Computational Method to Quantify the Effects of Slipped Strand Mispairing on Bacterial Tetranucleotide Repeats. Sci Rep 2019; 9:18087. [PMID: 31792233 PMCID: PMC6889271 DOI: 10.1038/s41598-019-53866-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 11/04/2019] [Indexed: 01/17/2023] Open
Abstract
The virulence and pathogenicity of bacterial pathogens are related to their adaptability to changing environments. One process enabling adaptation is based on minor changes in genome sequence, as small as a few base pairs, within segments of genome called simple sequence repeats (SSRs) that consist of multiple copies of a short sequence (from one to several nucleotides), repeated in series. SSRs are found in eukaryotes as well as prokaryotes, and length variation in them occurs at frequencies up to a million-fold higher than bacterial point mutations through the process of slipped strand mispairing (SSM) by DNA polymerase during replication. The characterization of SSR length by standard sequencing methods is complicated by the appearance of length variation introduced during the sequencing process that obscures the lower abundance repeat number variants in a population. Here we report a computational approach to correct for sequencing process-induced artifacts, validated for tetranucleotide repeats by use of synthetic constructs of fixed, known length. We apply this method to a laboratory culture of Histophilus somni, prepared from a single colony, and demonstrate that the culture consists of populations of distinct sequence phase and length variants at individual tetranucleotide SSR loci.
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Affiliation(s)
- Gregory P Harhay
- USDA ARS US Meat Animal Research Center, Clay Center, NE, United States.
| | - Dayna M Harhay
- USDA ARS US Meat Animal Research Center, Clay Center, NE, United States
| | - James L Bono
- USDA ARS US Meat Animal Research Center, Clay Center, NE, United States
| | - Sarah F Capik
- Texas A&M AgriLife Research, Amarillo, TX and the College of Veterinary Medicine & Biomedical Sciences, Texas A&M University System, College Station, TX, United States
| | - Keith D DeDonder
- Veterinary and Biomedical Research Center, Inc, Manhattan, KS, United States
| | - Michael D Apley
- Kansas State University, College of Veterinary Medicine, Manhattan, KS, United States
| | - Brian V Lubbers
- Kansas State University, College of Veterinary Medicine, Manhattan, KS, United States
| | - Bradley J White
- Kansas State University, College of Veterinary Medicine, Manhattan, KS, United States
| | - Robert L Larson
- Kansas State University, College of Veterinary Medicine, Manhattan, KS, United States
| | - Timothy P L Smith
- USDA ARS US Meat Animal Research Center, Clay Center, NE, United States
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10
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Abstract
In all domains of life, genomes contain epigenetic information superimposed over the nucleotide sequence. Epigenetic signals control DNA-protein interactions and can cause phenotypic change in the absence of mutation. A nearly universal mechanism of epigenetic signalling is DNA methylation. In bacteria, DNA methylation has roles in genome defence, chromosome replication and segregation, nucleoid organization, cell cycle control, DNA repair and regulation of transcription. In many bacterial species, DNA methylation controls reversible switching (phase variation) of gene expression, a phenomenon that generates phenotypic cell variants. The formation of epigenetic lineages enables the adaptation of bacterial populations to harsh or changing environments and modulates the interaction of pathogens with their eukaryotic hosts.
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11
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Garrett EM, Sekulovic O, Wetzel D, Jones JB, Edwards AN, Vargas-Cuebas G, McBride SM, Tamayo R. Phase variation of a signal transduction system controls Clostridioides difficile colony morphology, motility, and virulence. PLoS Biol 2019; 17:e3000379. [PMID: 31658249 PMCID: PMC6837544 DOI: 10.1371/journal.pbio.3000379] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Revised: 11/07/2019] [Accepted: 10/15/2019] [Indexed: 12/20/2022] Open
Abstract
Recent work has revealed that Clostridioides difficile, a major cause of nosocomial diarrheal disease, exhibits phenotypic heterogeneity within a clonal population as a result of phase variation. Many C. difficile strains representing multiple ribotypes develop two colony morphotypes, termed rough and smooth, but the biological implications of this phenomenon have not been explored. Here, we examine the molecular basis and physiological relevance of the distinct colony morphotypes produced by this bacterium. We show that C. difficile reversibly differentiates into rough and smooth colony morphologies and that bacteria derived from the isolates display discrete motility behaviors. We identified an atypical phase-variable signal transduction system consisting of a histidine kinase and two response regulators, named herein colony morphology regulators RST (CmrRST), which mediates the switch in colony morphology and motility behaviors. The CmrRST-regulated surface motility is independent of flagella and type IV pili, suggesting a novel mechanism of cell migration in C. difficile. Microscopic analysis of cell and colony structure indicates that CmrRST promotes the formation of elongated bacteria arranged in bundled chains, which may contribute to bacterial migration on surfaces. In a hamster model of acute C. difficile disease, the CmrRST system is required for disease development. Furthermore, we provide evidence that CmrRST phase varies during infection, suggesting that the intestinal environment impacts the proportion of CmrRST-expressing C. difficile. Our findings indicate that C. difficile employs phase variation of the CmrRST signal transduction system to generate phenotypic heterogeneity during infection, with concomitant effects on bacterial physiology and pathogenesis.
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Affiliation(s)
- Elizabeth M. Garrett
- Department of Microbiology and Immunology, University of North Carolina Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Ognjen Sekulovic
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Daniela Wetzel
- Department of Microbiology and Immunology, Emory University, Rollins Research Center, Atlanta, Georgia, United States of America
| | - Joshua B. Jones
- Department of Microbiology and Immunology, Emory University, Rollins Research Center, Atlanta, Georgia, United States of America
| | - Adrianne N. Edwards
- Department of Microbiology and Immunology, Emory University, Rollins Research Center, Atlanta, Georgia, United States of America
| | - Germán Vargas-Cuebas
- Department of Microbiology and Immunology, Emory University, Rollins Research Center, Atlanta, Georgia, United States of America
| | - Shonna M. McBride
- Department of Microbiology and Immunology, Emory University, Rollins Research Center, Atlanta, Georgia, United States of America
| | - Rita Tamayo
- Department of Microbiology and Immunology, University of North Carolina Chapel Hill, Chapel Hill, North Carolina, United States of America
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12
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Green LR, Dave N, Adewoye AB, Lucidarme J, Clark SA, Oldfield NJ, Turner DPJ, Borrow R, Bayliss CD. Potentiation of Phase Variation in Multiple Outer-Membrane Proteins During Spread of the Hyperinvasive Neisseria meningitidis Serogroup W ST-11 Lineage. J Infect Dis 2019; 220:1109-1117. [PMID: 31119276 PMCID: PMC6735796 DOI: 10.1093/infdis/jiz275] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 05/21/2019] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND Since 2009, increases in the incidence of invasive meningococcal disease have occurred in the United Kingdom due to a sublineage of the Neisseria meningitidis serogroup W ST-11 clonal complex (hereafter, the "original UK strain"). In 2013, a descendent substrain (hereafter, the "2013 strain") became the dominant disease-causing variant. Multiple outer-membrane proteins of meningococci are subject to phase-variable switches in expression due to hypermutable simple-sequence repeats. We investigated whether alterations in phase-variable genes may have influenced the relative prevalence of the original UK and 2013 substrains, using multiple disease and carriage isolates. METHODS Repeat numbers were determined by either bioinformatics analysis of whole-genome sequencing data or polymerase chain reaction amplification and sizing of fragments from genomic DNA extracts. Immunoblotting and sequence-translation analysis was performed to identify expression states. RESULTS Significant increases in repeat numbers were detected between the original UK and 2013 strains in genes encoding PorA, NadA, and 2 Opa variants. Invasive and carriage isolates exhibited similar repeat numbers, but the absence of pilC gene expression was frequently associated with disease. CONCLUSIONS Elevated repeat numbers in outer-membrane protein genes of the 2013 strain are indicative of higher phase-variation rates, suggesting that rapid expansion of this strain was due to a heightened ability to evade host immune responses during transmission and asymptomatic carriage.
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Affiliation(s)
- Luke R Green
- Department of Genetics and Genome Biology, University of Leicester, Leicester
| | - Neelam Dave
- Department of Genetics and Genome Biology, University of Leicester, Leicester
| | - Adeolu B Adewoye
- Department of Genetics and Genome Biology, University of Leicester, Leicester
| | - Jay Lucidarme
- Meningococcal Reference Unit, Public Health England, Manchester Royal Infirmary, Manchester
| | - Stephen A Clark
- Meningococcal Reference Unit, Public Health England, Manchester Royal Infirmary, Manchester
| | - Neil J Oldfield
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - David P J Turner
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Ray Borrow
- Meningococcal Reference Unit, Public Health England, Manchester Royal Infirmary, Manchester
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13
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Jensen TØ, Tellgren-Roth C, Redl S, Maury J, Jacobsen SAB, Pedersen LE, Nielsen AT. Genome-wide systematic identification of methyltransferase recognition and modification patterns. Nat Commun 2019; 10:3311. [PMID: 31427571 PMCID: PMC6700114 DOI: 10.1038/s41467-019-11179-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 06/27/2019] [Indexed: 01/25/2023] Open
Abstract
Genome-wide analysis of DNA methylation patterns using single molecule real-time DNA sequencing has boosted the number of publicly available methylomes. However, there is a lack of tools coupling methylation patterns and the corresponding methyltransferase genes. Here we demonstrate a high-throughput method for coupling methyltransferases with their respective motifs, using automated cloning and analysing the methyltransferases in vectors carrying a strain-specific cassette containing all potential target sites. To validate the method, we analyse the genomes of the thermophile Moorella thermoacetica and the mesophile Acetobacterium woodii, two acetogenic bacteria having substantially modified genomes with 12 methylation motifs and a total of 23 methyltransferase genes. Using our method, we characterize the 23 methyltransferases, assign motifs to the respective enzymes and verify activity for 11 of the 12 motifs. Single molecule real-time DNA sequencing allows genome-wide identification of DNA methylation patterns. Here, Jensen et al. present a high-throughput method that allows rapid coupling of DNA methylation patterns with their corresponding methyltransferase genes in bacteria.
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Affiliation(s)
- Torbjørn Ølshøj Jensen
- The Novo Nordisk Foundation Center for Biosustainability (CfB), Technical University of Denmark (DTU), DK-2800, Lyngby, Denmark
| | - Christian Tellgren-Roth
- Uppsala Genome Center, National Genomics Infrastructure, SciLifeLab, SE-751 08, Uppsala, Sweden
| | - Stephanie Redl
- The Novo Nordisk Foundation Center for Biosustainability (CfB), Technical University of Denmark (DTU), DK-2800, Lyngby, Denmark.,Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Jérôme Maury
- The Novo Nordisk Foundation Center for Biosustainability (CfB), Technical University of Denmark (DTU), DK-2800, Lyngby, Denmark
| | | | - Lasse Ebdrup Pedersen
- The Novo Nordisk Foundation Center for Biosustainability (CfB), Technical University of Denmark (DTU), DK-2800, Lyngby, Denmark
| | - Alex Toftgaard Nielsen
- The Novo Nordisk Foundation Center for Biosustainability (CfB), Technical University of Denmark (DTU), DK-2800, Lyngby, Denmark.
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14
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Turkington CJR, Morozov A, Clokie MRJ, Bayliss CD. Phage-Resistant Phase-Variant Sub-populations Mediate Herd Immunity Against Bacteriophage Invasion of Bacterial Meta-Populations. Front Microbiol 2019; 10:1473. [PMID: 31333609 PMCID: PMC6625227 DOI: 10.3389/fmicb.2019.01473] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2019] [Accepted: 06/13/2019] [Indexed: 01/06/2023] Open
Abstract
Hypermutable loci are widespread in bacteria as mechanisms for rapid generation of phenotypic diversity within a population that enables survival of fluctuating, often antagonistic, selection pressures. Localized hypermutation can mediate phase variation and enable survival of bacteriophage predation due to high frequency, reversible alterations in the expression of phage receptors. As phase variation can also generate population-to-population heterogeneity, we hypothesized that this phenomenon may facilitate survival of spatially-separated bacterial populations from phage invasion in a manner analogous to herd immunity to infectious diseases in human populations. The lic2A gene of Haemophilus influenzae is subject to “ON” and “OFF” switches in expression mediated by mutations in a 5′CAAT repeat tract present within the reading frame. The enzyme encoded by lic2A mediates addition of a galactose moiety of the lipopolysaccharide. This moiety is required for attachment of the HP1C1 phage such that the ON state of the lic2A gene is associated with HP1c1 susceptibility while the OFF state is resistant to infection. We developed an “oscillating prey assay” to examine phage spread through a series of sub-populations of Haemophilus influenzae whose phage receptor is in an ON or OFF state. Phage extinction was frequently observed when the proportion of phage-resistant sub-populations exceeded 34%. In silico modeling indicated that phage extinction was interdependent on phage loss during transfer between sub-populations and the frequency of resistant sub-populations. In a fixed-area oscillating prey assay, heterogeneity in phage resistance was observed to generate vast differences in phage densities across a meta-population of multiple bacterial sub-populations resulting in protective quarantining of some sub-populations from phage attack. We conclude that phase-variable hypermutable loci produce bacterial “herd immunity” with resistant intermediary-populations acting as a barricade to reduce the viral load faced by phage-susceptible sub-populations. This paradigm of meta-population protection is applicable to evolution of hypermutable loci in multiple bacteria-phage and host-pathogen interactions.
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Affiliation(s)
| | - Andrew Morozov
- Department of Mathematics, University of Leicester, Leicester, United Kingdom
| | - Martha R J Clokie
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom
| | - Christopher D Bayliss
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom
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15
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Nontypeable Haemophilus influenzae Invasive Blood Isolates Are Mainly Phosphorylcholine Negative and Show Decreased Complement-Mediated Killing That Is Associated with Lower Binding of IgM and CRP in Comparison to Colonizing Isolates from the Oropharynx. Infect Immun 2019; 87:IAI.00604-18. [PMID: 30455196 DOI: 10.1128/iai.00604-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 11/09/2018] [Indexed: 11/20/2022] Open
Abstract
Nontypeable Haemophilus influenzae (NTHi) bacteria express various molecules that contribute to their virulence. The presence of phosphocholine (PCho) on NTHi lipooligosaccharide increases adhesion to epithelial cells and is an advantage for the bacterium, enabling nasopharyngeal colonization, as measured in humans and animal models. However, when PCho is expressed on the lipooligosaccharide, it is also recognized by the acute-phase protein C-reactive protein (CRP) and PCho-specific antibodies, both of which are potent initiators of the classical pathway of complement activation. In this study, we show that blood isolates, which are exposed to CRP and PCho-specific antibodies in the bloodstream, have a higher survival in serum than oropharyngeal isolates, which was associated with a decreased presence of PCho. PCholow strains showed decreased IgM, CRP, and complement C3 deposition, which was associated with increased survival in human serum. Consistent with the case for the PCholow strains, removal of PCho expression by licA gene deletion decreased IgM, CRP, and complement C3 deposition, which increased survival in human serum. Complement-mediated killing of PChohigh strains was mainly dependent on binding of IgM to the bacterial surface. These data support the hypothesis that a PCholow phenotype was selected in blood during invasive disease, which increased resistance to serum killing, mainly due to lowered IgM and CRP binding to the bacterial surface.
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16
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Green LR, Haigh RD, Bayliss CD. Determination of Repeat Number and Expression States of Phase-Variable Loci Through Next Generation Sequencing and Bioinformatic Analysis. Methods Mol Biol 2019; 1969:83-92. [PMID: 30877670 DOI: 10.1007/978-1-4939-9202-7_5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Phase variation (PV) enables high frequency, reversible switches in expression of genetic loci across numerous species of bacteria. A major mechanism of PV in bacteria is the use of slipped strand mispairing across simple sequence repeats (SSRs). The generation and online availability of genomic datasets enables a comprehensive analysis of the distribution and composition of SSRs across multiple bacterial genomes of a species. PhasomeIt is a program that was developed to rapidly identify SSRs, to determine whether these SSRs mediate PV and to find homologous PV loci across multiple genomes. We describe use of this program for analysis of neisserial genomes. We further describe a method to reassemble specific PV loci to allow analysis of large repeat tracts which are often poorly assembled due to inherent drawbacks of the Illumina next generation sequencing (NGS) platform. These methodologies allow for rapid analysis of a major mechanism of PV across numerous species of Neisseria and other bacterial species.
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Affiliation(s)
- Luke R Green
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
| | - Richard D Haigh
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
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17
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Aidley J, Wanford JJ, Green LR, Sheppard SK, Bayliss CD. PhasomeIt: an 'omics' approach to cataloguing the potential breadth of phase variation in the genus Campylobacter. Microb Genom 2018; 4:e000228. [PMID: 30351264 PMCID: PMC6321876 DOI: 10.1099/mgen.0.000228] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 09/13/2018] [Indexed: 11/18/2022] Open
Abstract
Hypermutable simple sequence repeats (SSRs) are drivers of phase variation (PV) whose stochastic, high-frequency, reversible switches in gene expression are a common feature of several pathogenic bacterial species, including the human pathogen Campylobacter jejuni. Here we examine the distribution and conservation of known and putative SSR-driven phase variable genes - the phasome - in the genus Campylobacter. PhasomeIt, a new program, was specifically designed for rapid identification of SSR-mediated PV. This program detects the location, type and repeat number of every SSR. Each SSR is linked to a specific gene and its putative expression state. Other outputs include conservation of SSR-driven phase-variable genes and the 'core phasome' - the minimal set of PV genes in a phylogenetic grouping. Analysis of 77 complete Campylobacter genome sequences detected a 'core phasome' of conserved PV genes in each species and a large number of rare PV genes with few, or no, homologues in other genome sequences. Analysis of a set of partial genome sequences, with food-chain-associated metadata, detected evidence of a weak link between phasome and source host for disease-causing isolates of sequence type (ST)-828 but not the ST-21 or ST-45 complexes. Investigation of the phasomes in the genus Campylobacter provided evidence of overlapping but distinctive mechanisms of PV-mediated adaptation to specific niches. This suggests that the phasome could be involved in host adaptation and spread of campylobacters. Finally, this tool is malleable and will have utility for studying the distribution and genic effects of other repetitive elements in diverse bacterial species.
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Affiliation(s)
- Jack Aidley
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
| | - Joseph J. Wanford
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
| | - Luke R. Green
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
| | - Samuel K. Sheppard
- Milner Centre for Evolution, Department of Biology and Biochemistry, University of Bath, Bath, UK
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18
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Green LR, Lucidarme J, Dave N, Chan H, Clark S, Borrow R, Bayliss CD. Phase Variation of NadA in Invasive Neisseria meningitidis Isolates Impacts on Coverage Estimates for 4C-MenB, a MenB Vaccine. J Clin Microbiol 2018; 56:e00204-18. [PMID: 29950334 PMCID: PMC6113495 DOI: 10.1128/jcm.00204-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 06/19/2018] [Indexed: 11/20/2022] Open
Abstract
A recombinant NadA protein is one of the four major protective antigens of 4C-MenB (Bexsero), a vaccine developed for serogroup B Neisseria meningitidis (MenB). The meningococcal antigen typing system (MATS) is utilized as a high-throughput assay for assessing the invasive MenB strain coverage of 4C-MenB. Where present, the nadA gene is subject to phase-variable changes in transcription due to a 5'TAAA repeat tract located in a regulatory region. The promoter-containing intergenic region (IGR) sequences and 5'TAAA repeat numbers were determined for 906 invasive meningococcal disease isolates possessing the nadA gene. Exclusion of the 5'TAAA repeats reduced the number of IGR alleles from 82 to 23. Repeat numbers were associated with low and high levels of NadA expression by Western blotting and enzyme-linked immunosorbent assay (ELISA). Low-expression repeat numbers were present in 83% of 179 MenB isolates with NadA-2/3 or NadA-1 peptide variants and 68% of 480 MenW ST-11 complex isolates with NadA-2/3 peptide variants. For isolates with vaccine-compatible NadA variants, 93% of MATS-negative isolates were associated with low-expression repeat numbers, whereas 63% of isolates with MATS relative potency (RP) scores above the 95% confidence interval for the positive bactericidal threshold had high-expression repeat numbers. Analysis of 5'TAAA repeat numbers has potential as a rapid, high-throughput method for assessing strain coverage for the NadA component of 4C-MenB. A key application will be assessing coverage in meningococcal disease cases where confirmation is by PCR only and MATS cannot be applied.
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Affiliation(s)
- Luke R Green
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom
| | - Jay Lucidarme
- Meningococcal Reference Unit, Public Health England, Manchester Royal Infirmary, Manchester, United Kingdom
| | - Neelam Dave
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom
| | - Hannah Chan
- National Institute for Biological Standards and Control, Potters Bar, United Kingdom
| | - Stephen Clark
- Meningococcal Reference Unit, Public Health England, Manchester Royal Infirmary, Manchester, United Kingdom
| | - Ray Borrow
- Meningococcal Reference Unit, Public Health England, Manchester Royal Infirmary, Manchester, United Kingdom
| | - Christopher D Bayliss
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom
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19
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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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20
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Seib KL, Jen FEC, Scott AL, Tan A, Jennings MP. Phase variation of DNA methyltransferases and the regulation of virulence and immune evasion in the pathogenic Neisseria. Pathog Dis 2017; 75:3966716. [DOI: 10.1093/femspd/ftx080] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 07/13/2017] [Indexed: 01/31/2023] Open
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21
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Phase variation of Opa proteins of Neisseria meningitidis and the effects of bacterial transformation. J Biosci 2016; 41:13-9. [PMID: 26949083 DOI: 10.1007/s12038-016-9588-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Opa proteins are major proteins involved in meningococcal colonization of the nasopharynx and immune interactions. Opa proteins undergo phase variation (PV) due to the presence of the 5'-CTCTT-3' coding repeat (CR) sequence. The dynamics of PV of meningococcal Opa proteins is unknown. Opa PV, including the effect of transformation on PV, was assessed using a panel of Opa-deficient strains of Neisseria meningitidis. Analysis of Opa expression from UK disease-causing isolates was undertaken. Different opa genes demonstrated variable rates of PV, between 6.4 × 10(-4) and 6.9 × 10(-3) per cell per generation. opa genes with a longer CR tract had a higher rate of PV (r(2) = 0.77, p = 0.1212). Bacterial transformation resulted in a 180-fold increase in PV rate. The majority of opa genes in UK disease isolates (315/463, 68.0%) were in the 'on' phase, suggesting the importance of Opa proteins during invasive disease. These data provide valuable information for the first time regarding meningococcal Opa PV. The presence of Opa PV in meningococcal populations and high expression of Opa among invasive strains likely indicates the importance of this protein in bacterial colonization in the human nasopharynx. These findings have potential implications for development of vaccines derived from meningococcal outer membranes.
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22
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Siena E, D’Aurizio R, Riley D, Tettelin H, Guidotti S, Torricelli G, Moxon ER, Medini D. In-silico prediction and deep-DNA sequencing validation indicate phase variation in 115 Neisseria meningitidis genes. BMC Genomics 2016; 17:843. [PMID: 27793092 PMCID: PMC5084427 DOI: 10.1186/s12864-016-3185-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 10/22/2016] [Indexed: 01/25/2023] Open
Abstract
BACKGROUND The Neisseria meningitidis (Nm) chromosome shows a high abundance of simple sequence DNA repeats (SSRs) that undergo stochastic, reversible mutations at high frequency. This mechanism is reflected in an extensive phenotypic diversity that facilitates Nm adaptation to dynamic environmental changes. To date, phase-variable phenotypes mediated by SSRs variation have been experimentally confirmed for 26 Nm genes. RESULTS Here we present a population-scale comparative genomic analysis that identified 277 genes and classified them into 52 strong, 60 moderate and 165 weak candidates for phase variation. Deep-coverage DNA sequencing of single colonies grown overnight under non-selective conditions confirmed the presence of high-frequency, stochastic variation in 115 of them, providing circumstantial evidence for their phase variability. We confirmed previous observations of a predominance of variable SSRs within genes for components located on the cell surface or DNA metabolism. However, in addition we identified an unexpectedly broad spectrum of other metabolic functions, and most of the variable SSRs were predicted to induce phenotypic changes by modulating gene expression at a transcriptional level or by producing different protein isoforms rather than mediating on/off translational switching through frameshifts. Investigation of the evolutionary history of SSR contingency loci revealed that these loci were inherited from a Nm ancestor, evolved independently within Nm, or were acquired by Nm through lateral DNA exchange. CONCLUSIONS Overall, our results have identified a broader and qualitatively different phenotypic diversification of SSRs-mediated stochastic variation than previously documented, including its impact on central Nm metabolism.
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Affiliation(s)
| | - Romina D’Aurizio
- GSK Vaccines, 53100 Siena, Italy
- Present address: Institute of Informatics and Telematics and Institute of Clinical Physiology, National Research Council, 56124 Pisa, Italy
| | - David Riley
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD 21201 USA
- Present address: Personal Genome Disgnostics inc., Baltimore, MD 21224 USA
| | - Hervé Tettelin
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD 21201 USA
| | | | | | - E. Richard Moxon
- Medical Sciences Division, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, OX3 9DS UK
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23
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van Houte S, Buckling A, Westra ER. Evolutionary Ecology of Prokaryotic Immune Mechanisms. Microbiol Mol Biol Rev 2016; 80:745-63. [PMID: 27412881 PMCID: PMC4981670 DOI: 10.1128/mmbr.00011-16] [Citation(s) in RCA: 155] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Bacteria have a range of distinct immune strategies that provide protection against bacteriophage (phage) infections. While much has been learned about the mechanism of action of these defense strategies, it is less clear why such diversity in defense strategies has evolved. In this review, we discuss the short- and long-term costs and benefits of the different resistance strategies and, hence, the ecological conditions that are likely to favor the different strategies alone and in combination. Finally, we discuss some of the broader consequences, beyond resistance to phage and other genetic elements, resulting from the operation of different immune strategies.
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Affiliation(s)
- Stineke van Houte
- ESI and CEC, Department of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Angus Buckling
- ESI and CEC, Department of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Edze R Westra
- ESI and CEC, Department of Biosciences, University of Exeter, Exeter, United Kingdom
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24
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Ershova AS, Rusinov IS, Spirin SA, Karyagina AS, Alexeevski AV. Role of Restriction-Modification Systems in Prokaryotic Evolution and Ecology. BIOCHEMISTRY (MOSCOW) 2016; 80:1373-86. [PMID: 26567582 DOI: 10.1134/s0006297915100193] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Restriction-modification (R-M) systems are able to methylate or cleave DNA depending on methylation status of their recognition site. It allows them to protect bacterial cells from invasion by foreign DNA. Comparative analysis of a large number of available bacterial genomes and methylomes clearly demonstrates that the role of R-M systems in bacteria is wider than only defense. R-M systems maintain heterogeneity of a bacterial population and are involved in adaptation of bacteria to change in their environmental conditions. R-M systems can be essential for host colonization by pathogenic bacteria. Phase variation and intragenomic recombinations are sources of the fast evolution of the specificity of R-M systems. This review focuses on the influence of R-M systems on evolution and ecology of prokaryotes.
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Affiliation(s)
- A S Ershova
- Belozerksy Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
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25
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Brockman KL, Jurcisek JA, Atack JM, Srikhanta YN, Jennings MP, Bakaletz LO. ModA2 Phasevarion Switching in Nontypeable Haemophilus influenzae Increases the Severity of Experimental Otitis Media. J Infect Dis 2016; 214:817-24. [PMID: 27288538 DOI: 10.1093/infdis/jiw243] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 05/31/2016] [Indexed: 12/11/2022] Open
Abstract
Several human-adapted bacterial pathogens use a phasevarion (ie, a phase-variable regulon) to rapidly and reversibly regulate the expression of many genes, which include known virulence factors, yet the influence of phasevarion-mediated regulation in pathogenesis remains poorly understood. Here we examine the impact of the nontypeable Haemophilus influenzae (NTHI) ModA2 phasevarion on pathogenesis and disease severity in a chinchilla model of experimental otitis media. Chinchillas were challenged with NTHI variant populations that were either inoculated ON and remained ON, inoculated OFF and shifted ON, or inoculated OFF and remained OFF, within the middle ear. We show that populations that shift from OFF to ON within the middle ear induce significantly greater disease severity than populations that are unable to shift. These observations support the importance of phasevarion switching in NTHI pathogenesis and the necessity to considered phasevarion regulation when developing methods to treat and prevent infection.
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Affiliation(s)
- Kenneth L Brockman
- Center for Microbial Pathogenesis, The Research Institute at Nationwide Children's Hospital The Ohio State University College of Medicine, Columbus, Ohio
| | - Joseph A Jurcisek
- Center for Microbial Pathogenesis, The Research Institute at Nationwide Children's Hospital The Ohio State University College of Medicine, Columbus, Ohio
| | - John M Atack
- Institute for Glycomics, Griffith University, Gold Coast, Australia
| | | | | | - Lauren O Bakaletz
- Center for Microbial Pathogenesis, The Research Institute at Nationwide Children's Hospital The Ohio State University College of Medicine, Columbus, Ohio
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26
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Blow MJ, Clark TA, Daum CG, Deutschbauer AM, Fomenkov A, Fries R, Froula J, Kang DD, Malmstrom RR, Morgan RD, Posfai J, Singh K, Visel A, Wetmore K, Zhao Z, Rubin EM, Korlach J, Pennacchio LA, Roberts RJ. The Epigenomic Landscape of Prokaryotes. PLoS Genet 2016; 12:e1005854. [PMID: 26870957 PMCID: PMC4752239 DOI: 10.1371/journal.pgen.1005854] [Citation(s) in RCA: 220] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 01/19/2016] [Indexed: 11/18/2022] Open
Abstract
DNA methylation acts in concert with restriction enzymes to protect the integrity of prokaryotic genomes. Studies in a limited number of organisms suggest that methylation also contributes to prokaryotic genome regulation, but the prevalence and properties of such non-restriction-associated methylation systems remain poorly understood. Here, we used single molecule, real-time sequencing to map DNA modifications including m6A, m4C, and m5C across the genomes of 230 diverse bacterial and archaeal species. We observed DNA methylation in nearly all (93%) organisms examined, and identified a total of 834 distinct reproducibly methylated motifs. This data enabled annotation of the DNA binding specificities of 620 DNA Methyltransferases (MTases), doubling known specificities for previously hard to study Type I, IIG and III MTases, and revealing their extraordinary diversity. Strikingly, 48% of organisms harbor active Type II MTases with no apparent cognate restriction enzyme. These active ‘orphan’ MTases are present in diverse bacterial and archaeal phyla and show motif specificities and methylation patterns consistent with functions in gene regulation and DNA replication. Our results reveal the pervasive presence of DNA methylation throughout the prokaryotic kingdoms, as well as the diversity of sequence specificities and potential functions of DNA methylation systems. DNA methylation is a chemical modification of DNA present in many prokaryotic genomes. The best-known role of DNA methylation is as a component of restriction-modification systems. In these systems, restriction enzymes target foreign DNA for cleavage, while DNA methylation protects the host genome from destruction. Studies in a handful of organisms show that DNA methylation may also act independently of restriction systems and function in genome regulation. However, a lack of technologies has limited the study of DNA methylation to a small number of organisms, and the broader patterns and functions of DNA methylation remain unknown. Here we use SMRT-sequencing to determine the genome wide DNA methylation patterns of more than 200 diverse bacteria and archaea. We show that DNA methylation is pervasive and present in more than 90% of studied organisms. Analysis of this data enabled annotation of the specific DNA binding sites of more than 600 restriction systems, revealing their extraordinary diversity. Strikingly, we observed widespread DNA methylation in the absence of restriction systems. Analyses of these patterns reveal that they are conserved through evolution, and likely function in genome regulation. Thus DNA methylation may play a far wider function in prokaryotic genome biology than was previously supposed.
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Affiliation(s)
- Matthew J. Blow
- Genomics Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- U.S. Department of Energy Joint Genome Institute, Walnut Creek, California, United States of America
- * E-mail: (MJB); (RJR)
| | - Tyson A. Clark
- Pacific Biosciences, Menlo Park, California, United States of America
| | - Chris G. Daum
- Genomics Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- U.S. Department of Energy Joint Genome Institute, Walnut Creek, California, United States of America
| | - Adam M. Deutschbauer
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Alexey Fomenkov
- New England Biolabs, Ipswich, Massachusetts, United States of America
| | - Roxanne Fries
- Genomics Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- U.S. Department of Energy Joint Genome Institute, Walnut Creek, California, United States of America
| | - Jeff Froula
- Genomics Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- U.S. Department of Energy Joint Genome Institute, Walnut Creek, California, United States of America
| | - Dongwan D. Kang
- Genomics Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- U.S. Department of Energy Joint Genome Institute, Walnut Creek, California, United States of America
| | - Rex R. Malmstrom
- Genomics Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- U.S. Department of Energy Joint Genome Institute, Walnut Creek, California, United States of America
| | - Richard D. Morgan
- New England Biolabs, Ipswich, Massachusetts, United States of America
| | - Janos Posfai
- New England Biolabs, Ipswich, Massachusetts, United States of America
| | - Kanwar Singh
- Genomics Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- U.S. Department of Energy Joint Genome Institute, Walnut Creek, California, United States of America
| | - Axel Visel
- Genomics Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- U.S. Department of Energy Joint Genome Institute, Walnut Creek, California, United States of America
| | - Kelly Wetmore
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Zhiying Zhao
- Genomics Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- U.S. Department of Energy Joint Genome Institute, Walnut Creek, California, United States of America
| | - Edward M. Rubin
- Genomics Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- U.S. Department of Energy Joint Genome Institute, Walnut Creek, California, United States of America
| | - Jonas Korlach
- Pacific Biosciences, Menlo Park, California, United States of America
| | - Len A. Pennacchio
- Genomics Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- U.S. Department of Energy Joint Genome Institute, Walnut Creek, California, United States of America
| | - Richard J. Roberts
- New England Biolabs, Ipswich, Massachusetts, United States of America
- * E-mail: (MJB); (RJR)
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27
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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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28
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Kwiatek A, Mrozek A, Bacal P, Piekarowicz A, Adamczyk-Popławska M. Type III Methyltransferase M.NgoAX from Neisseria gonorrhoeae FA1090 Regulates Biofilm Formation and Interactions with Human Cells. Front Microbiol 2015; 6:1426. [PMID: 26733970 PMCID: PMC4685087 DOI: 10.3389/fmicb.2015.01426] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Accepted: 11/30/2015] [Indexed: 11/24/2022] Open
Abstract
Neisseria gonorrhoeae is the etiological factor of the sexually transmitted gonorrhea disease that may lead, under specific conditions, to systemic infections. The gonococcal genome encodes many restriction modification (RM) systems, which main biological role is to defend the pathogen from potentially harmful foreign DNA. However, RM systems seem also to be involved in several other functions. In this study, we examined the effect of inactivation the N. gonorrhoeae FA1090 ngoAXmod gene encoding M.NgoAX methyltransferase on the global gene expression, biofilm formation, interactions with human epithelial host cells and overall bacterial growth. Expression microarrays showed at least a twofold deregulation of a total of 121 genes in the NgoAX knock-out mutant compared to the wild-type (wt) strain under standard grow conditions. Genes with changed expression levels encoded mostly proteins involved in cell metabolism, DNA replication and repair or regulating cellular processes and signaling (such as cell wall/envelop biogenesis). As determined by the assay with crystal violet, the NgoAX knock-out strain formed a slightly larger biofilm biomass per cell than the wt strain. Live biofilm observations showed that the biofilm formed by the gonococcal ngoAXmod gene mutant is more relaxed, dispersed and thicker than the one formed by the wt strain. This more relaxed feature of the biofilm, in respect to adhesion and bacterial interactions, can be involved in pathogenesis. Moreover, the overall adhesion of mutant bacterial cells to human cells was lower than adhesion of the wt gonococci [adhesion index = 0.672 (±0.2) and 2.15 (±1.53), respectively]; yet, a higher number of mutant than wt bacteria were found inside the Hec-1-B epithelial cells [invasion index = 3.38 (±0.93) × 105 for mutant and 4.67 (±3.09) × 104 for the wt strain]. These results indicate that NgoAX knock-out cells have lower ability to attach to human cells, but more easily penetrate inside the host cells. All these data suggest that the NgoAX methyltransferase, may be implicated in N. gonorrhoeae pathogenicity, involving regulation of biofilm formation, adhesion to host cells and epithelial cell invasion.
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Affiliation(s)
- Agnieszka Kwiatek
- Institute of Microbiology, Faculty of Biology, University of Warsaw Warsaw, Poland
| | - Agnieszka Mrozek
- Institute of Microbiology, Faculty of Biology, University of Warsaw Warsaw, Poland
| | - Pawel Bacal
- Laboratory of Theory and Applications of Electrodes, Faculty of Chemistry, University of Warsaw Warsaw, Poland
| | - Andrzej Piekarowicz
- Institute of Microbiology, Faculty of Biology, University of Warsaw Warsaw, Poland
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Kell D, Potgieter M, Pretorius E. Individuality, phenotypic differentiation, dormancy and 'persistence' in culturable bacterial systems: commonalities shared by environmental, laboratory, and clinical microbiology. F1000Res 2015; 4:179. [PMID: 26629334 PMCID: PMC4642849 DOI: 10.12688/f1000research.6709.2] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/04/2015] [Indexed: 01/28/2023] Open
Abstract
For bacteria, replication mainly involves growth by binary fission. However, in a very great many natural environments there are examples of phenotypically dormant, non-growing cells that do not replicate immediately and that are phenotypically 'nonculturable' on media that normally admit their growth. They thereby evade detection by conventional culture-based methods. Such dormant cells may also be observed in laboratory cultures and in clinical microbiology. They are usually more tolerant to stresses such as antibiotics, and in clinical microbiology they are typically referred to as 'persisters'. Bacterial cultures necessarily share a great deal of relatedness, and inclusive fitness theory implies that there are conceptual evolutionary advantages in trading a variation in growth rate against its mean, equivalent to hedging one's bets. There is much evidence that bacteria exploit this strategy widely. We here bring together data that show the commonality of these phenomena across environmental, laboratory and clinical microbiology. Considerable evidence, using methods similar to those common in environmental microbiology, now suggests that many supposedly non-communicable, chronic and inflammatory diseases are exacerbated (if not indeed largely caused) by the presence of dormant or persistent bacteria (the ability of whose components to cause inflammation is well known). This dormancy (and resuscitation therefrom) often reflects the extent of the availability of free iron. Together, these phenomena can provide a ready explanation for the continuing inflammation common to such chronic diseases and its correlation with iron dysregulation. This implies that measures designed to assess and to inhibit or remove such organisms (or their access to iron) might be of much therapeutic benefit.
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Affiliation(s)
- Douglas Kell
- School of Chemistry and The Manchester Institute of Biotechnology, The University of Manchester, Manchester, Lancashire, M1 7DN, UK
| | - Marnie Potgieter
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Arcadia, 0007, South Africa
| | - Etheresia Pretorius
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Arcadia, 0007, South Africa
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30
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Kell D, Potgieter M, Pretorius E. Individuality, phenotypic differentiation, dormancy and 'persistence' in culturable bacterial systems: commonalities shared by environmental, laboratory, and clinical microbiology. F1000Res 2015; 4:179. [PMID: 26629334 DOI: 10.12688/f1000research.6709.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/29/2015] [Indexed: 01/28/2023] Open
Abstract
For bacteria, replication mainly involves growth by binary fission. However, in a very great many natural environments there are examples of phenotypically dormant, non-growing cells that do not replicate immediately and that are phenotypically 'nonculturable' on media that normally admit their growth. They thereby evade detection by conventional culture-based methods. Such dormant cells may also be observed in laboratory cultures and in clinical microbiology. They are usually more tolerant to stresses such as antibiotics, and in clinical microbiology they are typically referred to as 'persisters'. Bacterial cultures necessarily share a great deal of relatedness, and inclusive fitness theory implies that there are conceptual evolutionary advantages in trading a variation in growth rate against its mean, equivalent to hedging one's bets. There is much evidence that bacteria exploit this strategy widely. We here bring together data that show the commonality of these phenomena across environmental, laboratory and clinical microbiology. Considerable evidence, using methods similar to those common in environmental microbiology, now suggests that many supposedly non-communicable, chronic and inflammatory diseases are exacerbated (if not indeed largely caused) by the presence of dormant or persistent bacteria (the ability of whose components to cause inflammation is well known). This dormancy (and resuscitation therefrom) often reflects the extent of the availability of free iron. Together, these phenomena can provide a ready explanation for the continuing inflammation common to such chronic diseases and its correlation with iron dysregulation. This implies that measures designed to assess and to inhibit or remove such organisms (or their access to iron) might be of much therapeutic benefit.
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Affiliation(s)
- Douglas Kell
- School of Chemistry and The Manchester Institute of Biotechnology, The University of Manchester, Manchester, Lancashire, M1 7DN, UK
| | - Marnie Potgieter
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Arcadia, 0007, South Africa
| | - Etheresia Pretorius
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Arcadia, 0007, South Africa
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31
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Post DMB, Held JM, Ketterer MR, Phillips NJ, Sahu A, Apicella MA, Gibson BW. Comparative analyses of proteins from Haemophilus influenzae biofilm and planktonic populations using metabolic labeling and mass spectrometry. BMC Microbiol 2014; 14:329. [PMID: 25551439 PMCID: PMC4302520 DOI: 10.1186/s12866-014-0329-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 12/16/2014] [Indexed: 11/25/2022] Open
Abstract
Background Non-typeable H. influenzae (NTHi) is a nasopharyngeal commensal that can become an opportunistic pathogen causing infections such as otitis media, pneumonia, and bronchitis. NTHi is known to form biofilms. Resistance of bacterial biofilms to clearance by host defense mechanisms and antibiotic treatments is well-established. In the current study, we used stable isotope labeling by amino acids in cell culture (SILAC) to compare the proteomic profiles of NTHi biofilm and planktonic organisms. Duplicate continuous-flow growth chambers containing defined media with either “light” (L) isoleucine or “heavy” (H) 13C6-labeled isoleucine were used to grow planktonic (L) and biofilm (H) samples, respectively. Bacteria were removed from the chambers, mixed based on weight, and protein extracts were generated. Liquid chromatography-mass spectrometry (LC-MS) was performed on the tryptic peptides and 814 unique proteins were identified with 99% confidence. Results Comparisons of the NTHi biofilm to planktonic samples demonstrated that 127 proteins showed differential expression with p-values ≤0.05. Pathway analysis demonstrated that proteins involved in energy metabolism, protein synthesis, and purine, pyrimidine, nucleoside, and nucleotide processes showed a general trend of downregulation in the biofilm compared to planktonic organisms. Conversely, proteins involved in transcription, DNA metabolism, and fatty acid and phospholipid metabolism showed a general trend of upregulation under biofilm conditions. Selected reaction monitoring (SRM)-MS was used to validate a subset of these proteins; among these were aerobic respiration control protein ArcA, NAD nucleotidase and heme-binding protein A. Conclusions The present proteomic study indicates that the NTHi biofilm exists in a semi-dormant state with decreased energy metabolism and protein synthesis yet is still capable of managing oxidative stress and in acquiring necessary cofactors important for biofilm survival. Electronic supplementary material The online version of this article (doi:10.1186/s12866-014-0329-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Deborah M B Post
- The Buck Institute for Research on Aging, Novato, CA, 94945, USA.
| | - Jason M Held
- Washington University School of Medicine, St. Louis, MO, 63110, USA.
| | | | - Nancy J Phillips
- The University of California San Francisco, San Francisco, CA, 94143, USA.
| | - Alexandria Sahu
- The Buck Institute for Research on Aging, Novato, CA, 94945, USA.
| | | | - Bradford W Gibson
- The Buck Institute for Research on Aging, Novato, CA, 94945, USA. .,The University of California San Francisco, San Francisco, CA, 94143, USA.
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Abstract
Neisseria gonorrhoeae and Neisseria meningitidis are closely related organisms that cause the sexually transmitted infection gonorrhea and serious bacterial meningitis and septicemia, respectively. Both species possess multiple mechanisms to alter the expression of surface-exposed proteins through the processes of phase and antigenic variation. This potential for wide variability in surface-exposed structures allows the organisms to always have subpopulations of divergent antigenic types to avoid immune surveillance and to contribute to functional variation. Additionally, the Neisseria are naturally competent for DNA transformation, which is their main means of genetic exchange. Although bacteriophages and plasmids are present in this genus, they are not as effective as DNA transformation for horizontal genetic exchange. There are barriers to genetic transfer, such as restriction-modification systems and CRISPR loci, that limit particular types of exchange. These host-restricted pathogens illustrate the rich complexity of genetics that can help define the similarities and differences of closely related organisms.
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Affiliation(s)
- Ella Rotman
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611; ,
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Alfsnes K, Raynaud X, Tønjum T, Ambur OH. Mathematical and live meningococcal models for simple sequence repeat dynamics - coherent predictions and observations. PLoS One 2014; 9:e101637. [PMID: 24999629 PMCID: PMC4085013 DOI: 10.1371/journal.pone.0101637] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 06/10/2014] [Indexed: 11/18/2022] Open
Abstract
Evolvability by means of simple sequence repeat (SSR) instability is a feature under the constant influence of opposing selective pressures to expand and compress the repeat tract and is mechanistically influenced by factors that affect genetic instability. In addition to direct selection for protein expression and structural integrity, other factors that influence tract length evolution were studied. The genetic instability of SSRs that switch the expression of antibiotic resistance ON and OFF was modelled mathematically and monitored in a panel of live meningococcal strains. The mathematical model showed that the SSR length of a theoretical locus in an evolving population may be shaped by direct selection of expression status (ON or OFF), tract length dependent (α) and tract length independent factors (β). According to the model an increase in α drives the evolution towards shorter tracts. An increase in β drives the evolution towards a normal distribution of tract lengths given that an upper and a lower limit are set. Insertion and deletion biases were shown to skew allelic distributions in both directions. The meningococcal SSR model was tested in vivo by monitoring the frequency of spectinomycin resistance OFF→ON switching in a designed locus. The instability of a comprehensive panel of the homopolymeric SSRs, constituted of a range of 5-13 guanine nucleotides, was monitored in wildtype and mismatch repair deficient backgrounds. Both the repeat length itself and mismatch repair deficiency were shown to influence the genetic instability of the homopolymeric tracts. A possible insertion bias was observed in tracts ≤G10. Finally, an inverse correlation between the number of tract-encoded amino acids and growth in the presence of ON-selection illustrated a limitation to SSR expansion in an essential gene associated with the designed model locus and the protein function mediating antibiotic resistance.
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Affiliation(s)
- Kristian Alfsnes
- Department of Microbiology, University of Oslo, Oslo, Norway
- Department of Microbiology, Oslo University Hospital (Rikshospitalet), Oslo, Norway
| | - Xavier Raynaud
- Department of Mathematics, University of Oslo, Oslo, Norway
| | - Tone Tønjum
- Department of Microbiology, University of Oslo, Oslo, Norway
- Department of Microbiology, Oslo University Hospital (Rikshospitalet), Oslo, Norway
| | - Ole Herman Ambur
- Department of Microbiology, University of Oslo, Oslo, Norway
- Department of Microbiology, Oslo University Hospital (Rikshospitalet), Oslo, Norway
- Department of Microbiology and Infection Control, Akershus University Hospital, Lørenskog, Norway
- * E-mail:
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Davis GS, Marino S, Marrs CF, Gilsdorf JR, Dawid S, Kirschner DE. Phase variation and host immunity against high molecular weight (HMW) adhesins shape population dynamics of nontypeable Haemophilus influenzae within human hosts. J Theor Biol 2014; 355:208-18. [PMID: 24747580 DOI: 10.1016/j.jtbi.2014.04.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 03/21/2014] [Accepted: 04/04/2014] [Indexed: 12/16/2022]
Abstract
Nontypeable Haemophilus influenzae (NTHi) is a bacterium that resides within the human pharynx. Because NTHi is human-restricted, its long-term survival is dependent upon its ability to successfully colonize new hosts. Adherence to host epithelium, mediated by bacterial adhesins, is one of the first steps in NTHi colonization. NTHi express several adhesins, including the high molecular weight (HMW) adhesins that mediate attachment to the respiratory epithelium where they interact with the host immune system to elicit a strong humoral response. hmwA, which encodes the HMW adhesin, undergoes phase variation mediated by 7-base pair tandem repeats located within its promoter region. Repeat number affects both hmwA transcription and HMW-adhesin production such that as the number of repeats increases, adhesin production decreases. Cells expressing large amounts of HMW adhesins may be critical for the establishment and maintenance of NTHi colonization, but they might also incur greater fitness costs when faced with an adhesin-specific antibody-mediated immune response. We hypothesized that the occurrence of large deletion events within the hmwA repeat region allows NTHi cells to maintain adherence in the presence of antibody-mediated immunity. To study this, we developed a mathematical model, incorporating hmwA phase variation and antibody-mediated immunity, to explore the trade-off between bacterial adherence and immune evasion. The model predicts that antibody levels and avidity, catastrophic loss rates, and population carrying capacity all significantly affected numbers of adherent NTHi cells within a host. These results suggest that the occurrence of large, yet rare, deletion events allows for stable maintenance of a small population of adherent cells in spite of HMW adhesin specific antibody-mediated immunity. These adherent subpopulations may be important for sustaining colonization and/or maintaining transmission.
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Affiliation(s)
- Gregg S Davis
- Department of Epidemiology, University of Michigan School of Public Health, 1415 Washington Heights, Ann Arbor, MI 48109, USA.
| | - Simeone Marino
- Department of Microbiology and Immunology, University of Michigan Medical School, 1150 West Medical Center Drive, 5641 Med Sci II SPC 5620, Ann Arbor, MI 48109, USA.
| | - Carl F Marrs
- Department of Epidemiology, University of Michigan School of Public Health, 1415 Washington Heights, Ann Arbor, MI 48109, USA.
| | - Janet R Gilsdorf
- Department of Epidemiology, University of Michigan School of Public Health, 1415 Washington Heights, Ann Arbor, MI 48109, USA; Department of Pediatrics, University of Michigan Medical School, L2225 Women׳s Hospital, Ann Arbor, MI 48109, USA.
| | - Suzanne Dawid
- Department of Microbiology and Immunology, University of Michigan Medical School, 1150 West Medical Center Drive, 5641 Med Sci II SPC 5620, Ann Arbor, MI 48109, USA; UMHS Pediatric Infectious Diseases, University of Michigan Health System, D5101 MPB, Ann Arbor, MI 48109, USA.
| | - Denise E Kirschner
- Department of Microbiology and Immunology, University of Michigan Medical School, 1150 West Medical Center Drive, 5641 Med Sci II SPC 5620, Ann Arbor, MI 48109, USA.
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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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36
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Genomic and global approaches to unravelling how hypermutable sequences influence bacterial pathogenesis. Pathogens 2014; 3:164-84. [PMID: 25437613 PMCID: PMC4235727 DOI: 10.3390/pathogens3010164] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 01/06/2014] [Accepted: 02/13/2014] [Indexed: 12/23/2022] Open
Abstract
Rapid adaptation to fluctuations in the host milieu contributes to the host persistence and virulence of bacterial pathogens. Adaptation is frequently mediated by hypermutable sequences in bacterial pathogens. Early bacterial genomic studies identified the multiplicity and virulence-associated functions of these hypermutable sequences. Thus, simple sequence repeat tracts (SSRs) and site-specific recombination were found to control capsular type, lipopolysaccharide structure, pilin diversity and the expression of outer membrane proteins. We review how the population diversity inherent in the SSR-mediated mechanism of localised hypermutation is being unlocked by the investigation of whole genome sequences of disease isolates, analysis of clinical samples and use of model systems. A contrast is presented between the problematical nature of analysing simple sequence repeats in next generation sequencing data and in simpler, pragmatic PCR-based approaches. Specific examples are presented of the potential relevance of this localized hypermutation to meningococcal pathogenesis. This leads us to speculate on the future prospects for unravelling how hypermutable mechanisms may contribute to the transmission, spread and persistence of bacterial pathogens.
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Rao DN, Dryden DTF, Bheemanaik S. Type III restriction-modification enzymes: a historical perspective. Nucleic Acids Res 2014; 42:45-55. [PMID: 23863841 PMCID: PMC3874151 DOI: 10.1093/nar/gkt616] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 05/28/2013] [Accepted: 06/24/2013] [Indexed: 11/12/2022] Open
Abstract
Restriction endonucleases interact with DNA at specific sites leading to cleavage of DNA. Bacterial DNA is protected from restriction endonuclease cleavage by modifying the DNA using a DNA methyltransferase. Based on their molecular structure, sequence recognition, cleavage position and cofactor requirements, restriction-modification (R-M) systems are classified into four groups. Type III R-M enzymes need to interact with two separate unmethylated DNA sequences in inversely repeated head-to-head orientations for efficient cleavage to occur at a defined location (25-27 bp downstream of one of the recognition sites). Like the Type I R-M enzymes, Type III R-M enzymes possess a sequence-specific ATPase activity for DNA cleavage. ATP hydrolysis is required for the long-distance communication between the sites before cleavage. Different models, based on 1D diffusion and/or 3D-DNA looping, exist to explain how the long-distance interaction between the two recognition sites takes place. Type III R-M systems are found in most sequenced bacteria. Genome sequencing of many pathogenic bacteria also shows the presence of a number of phase-variable Type III R-M systems, which play a role in virulence. A growing number of these enzymes are being subjected to biochemical and genetic studies, which, when combined with ongoing structural analyses, promise to provide details for mechanisms of DNA recognition and catalysis.
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Affiliation(s)
- Desirazu N. Rao
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India and School of Chemistry, The King’s Buildings, The University of Edinburgh, Edinburgh EH9 3JJ, Scotland, UK
| | - David T. F. Dryden
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India and School of Chemistry, The King’s Buildings, The University of Edinburgh, Edinburgh EH9 3JJ, Scotland, UK
| | - Shivakumara Bheemanaik
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India and School of Chemistry, The King’s Buildings, The University of Edinburgh, Edinburgh EH9 3JJ, Scotland, UK
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Zhou K, Aertsen A, Michiels CW. The role of variable DNA tandem repeats in bacterial adaptation. FEMS Microbiol Rev 2013; 38:119-41. [PMID: 23927439 DOI: 10.1111/1574-6976.12036] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 07/13/2013] [Accepted: 07/26/2013] [Indexed: 01/05/2023] Open
Abstract
DNA tandem repeats (TRs), also designated as satellite DNA, are inter- or intragenic nucleotide sequences that are repeated two or more times in a head-to-tail manner. Because TR tracts are prone to strand-slippage replication and recombination events that cause the TR copy number to increase or decrease, loci containing TRs are hypermutable. An increasing number of examples illustrate that bacteria can exploit this instability of TRs to reversibly shut down or modulate the function of specific genes, allowing them to adapt to changing environments on short evolutionary time scales without an increased overall mutation rate. In this review, we discuss the prevalence and distribution of inter- and intragenic TRs in bacteria and the mechanisms of their instability. In addition, we review evidence demonstrating a role of TR variations in bacterial adaptation strategies, ranging from immune evasion and tissue tropism to the modulation of environmental stress tolerance. Nevertheless, while bioinformatic analysis reveals that most bacterial genomes contain a few up to several dozens of intra- and intergenic TRs, only a small fraction of these have been functionally studied to date.
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Affiliation(s)
- Kai Zhou
- Department of Microbial and Molecular Systems (M²S), Faculty of Bioscience Engineering, Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
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39
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Poole J, Foster E, Chaloner K, Hunt J, Jennings MP, Bair T, Knudtson K, Christensen E, Munson RS, Winokur PL, Apicella MA. Analysis of nontypeable haemophilus influenzae phase-variable genes during experimental human nasopharyngeal colonization. J Infect Dis 2013; 208:720-7. [PMID: 23715658 DOI: 10.1093/infdis/jit240] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Studies of nontypeable Haemophilus influenzae (NTHi) have demonstrated that a number of genes associated with infectivity have long repeat regions associated with phase variation in expression of the respective gene. The purpose of this study was to determine the genes that underwent phase variation during a 6-day period of experimental human nasopharyngeal colonization. METHODS Strain NTHi 2019Str(R)1 was used to colonize the nasopharynx of human subjects in a study of experimental colonization. Thirteen phase-variable genes were analyzed in NTHi 2019Str(R)1. Samples of NTHi 2019Str(R)1 were cultured from subjects during the 6-day colonization period. We used capillary electrophoresis and Roche 454 pyrosequencing to determine the number of repeats in each gene from each sample. RESULTS A significant number of samples switched licA and igaB from phase off in the inoculated strain to phase on during the 4-day period of observation. lex2A also showed variability as compared to baseline, but the differences were not significant. The remaining genes showed no evidence of phase variation. CONCLUSIONS Our studies suggest that the phase-on genotypes of licA and igaB are important for early human nasopharynx colonization. lex2A showed a trend from phase off to phase on, suggesting a potentially important role in the colonization process.
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Affiliation(s)
- Jessica Poole
- Department of Microbiology, University of Iowa, Iowa City, IA 52242, USA
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40
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Inzana TJ. Identification of phase-variable genes that may contribute to nontypeable haemophilus influenzae nasopharyngeal colonization in humans contributes to our understanding of specific host-pathogen interactions. J Infect Dis 2013; 208:713-6. [PMID: 23715662 DOI: 10.1093/infdis/jit243] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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41
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Vasu K, Nagaraja V. Diverse functions of restriction-modification systems in addition to cellular defense. Microbiol Mol Biol Rev 2013; 77:53-72. [PMID: 23471617 PMCID: PMC3591985 DOI: 10.1128/mmbr.00044-12] [Citation(s) in RCA: 376] [Impact Index Per Article: 34.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Restriction-modification (R-M) systems are ubiquitous and are often considered primitive immune systems in bacteria. Their diversity and prevalence across the prokaryotic kingdom are an indication of their success as a defense mechanism against invading genomes. However, their cellular defense function does not adequately explain the basis for their immaculate specificity in sequence recognition and nonuniform distribution, ranging from none to too many, in diverse species. The present review deals with new developments which provide insights into the roles of these enzymes in other aspects of cellular function. In this review, emphasis is placed on novel hypotheses and various findings that have not yet been dealt with in a critical review. Emerging studies indicate their role in various cellular processes other than host defense, virulence, and even controlling the rate of evolution of the organism. We also discuss how R-M systems could have successfully evolved and be involved in additional cellular portfolios, thereby increasing the relative fitness of their hosts in the population.
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Affiliation(s)
- Kommireddy Vasu
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore
| | - Valakunja Nagaraja
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore
- Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India
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42
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Chiang YT, Shien JH, Tan DH, Shieh MK, Liu CC, Chen YS, Chang PC. Identification of thelic1ABCDoperon that controls the phase-variable expression of phosphorylcholine on lipopolysaccharide fromAvibacterium paragallinarum. Avian Pathol 2013; 42:72-8. [DOI: 10.1080/03079457.2012.760840] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Y. T. Chiang
- a Graduate Institute of Microbiology and Public Health , National Chung Hsing University , Taichung , Taiwan
| | - J. H. Shien
- b Department of Veterinary Medicine , National Chung Hsing University , Taichung , Taiwan
| | - D. H. Tan
- a Graduate Institute of Microbiology and Public Health , National Chung Hsing University , Taichung , Taiwan
| | - M. K. Shieh
- a Graduate Institute of Microbiology and Public Health , National Chung Hsing University , Taichung , Taiwan
| | - C. C. Liu
- c Institute of Genomics and Bioinformatics, National Chung Hsing University , Taichung , Taiwan
| | - Y. S. Chen
- b Department of Veterinary Medicine , National Chung Hsing University , Taichung , Taiwan
| | - P. C. Chang
- a Graduate Institute of Microbiology and Public Health , National Chung Hsing University , Taichung , Taiwan
- d Agricultural Biotechnology Center , National Chung Hsing University , Taichung , Taiwan
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Abstract
Simple sequence repeat (SSR) tracts produce stochastic on-off switching, or phase variation, in the expression of a panoply of surface molecules in many bacterial commensals and pathogens. A change to the number of repeats in a tract may alter the phase of the translational reading frame, which toggles the on-off state of the switch. Here, we construct an in silico SSR locus with mutational dynamics calibrated to those of the Haemophilus influenzae mod locus. We simulate its evolution in a regimen of two alternating environments, simultaneously varying the selection coefficient, s, and the epoch length, T. Some recent work in a simpler (two-locus) model suggested that stochastic switching in a regimen of two alternating environments may be evolutionarily favored only if the selection coefficients in the two environments are nearly equal (“symmetric”) or selection is very strong. This finding was puzzling, as it greatly restricted the conditions under which stochastic switching might evolve. Instead, we find agreement with other recent theoretical work, observing selective utility for stochastic switching if the product sT is large enough for the favored state to nearly fix in both environments. Symmetry is required neither in s nor in sT. Because we simulate finite populations and use a detailed model of the SSR locus, we are also able to examine the impact of population size and of several SSR locus parameters. Our results indicate that conditions favoring evolution and maintenance of SSR loci in bacteria are quite broad. Bacteria experience frequent changes of environment during the infection cycle. One means to rapidly adapt is stochastic switching: a bacterial lineage will stochastically produce a variety of genotypes, so that some descendants will survive if the environment changes. Stochastic switching mediated by simple sequence repeat (SSR) loci is widespread among bacterial commensals and pathogens and influences critical interactions with host surfaces or immune effectors, thereby affecting host persistence, transmission, and virulence. Here, we use the most detailed in silico model of an SSR locus to date, with its phase variation calibrated to match the mod locus of Haemophilus influenzae. The type III restriction-modification system encoded by mod participates in the regulation of multiple other genes; thus, SSR-mediated phase variation of mod has far-reaching cis-regulatory effects. This coupling of phase-variable switching to complex phenotypic effects has been described as the “phasevarion” and is central to understanding the infection cycle of bacterial commensals and pathogens.
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Abstract
In prokaryotes, alteration in gene expression was observed with the modification of DNA, especially DNA methylation. Such changes are inherited from generation to generation with no alterations in the DNA sequence and represent the epigenetic signal in prokaryotes. DNA methyltransferases are enzymes involved in DNA modification and thus in epigenetic regulation of gene expression. DNA methylation not only affects the thermodynamic stability of DNA, but also changes its curvature. Methylation of specific residues on DNA can affect the protein-DNA interactions. DNA methylation in prokaryotes regulates a number of physiological processes in the bacterial cell including transcription, DNA mismatch repair and replication initiation. Significantly, many reports have suggested a role of DNA methylation in regulating the expression of a number of genes in virulence and pathogenesis thus, making DNA methlytransferases novel targets for the designing of therapeutics. Here, we summarize the current knowledge about the influence of DNA methylation on gene regulation in different bacteria, and on bacterial virulence.
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Affiliation(s)
- Ritesh Kumar
- Department of Biochemistry, Indian Institute of Science, Bangalore, 560012, India,
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45
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Bayliss CD, Palmer ME. Evolution of simple sequence repeat-mediated phase variation in bacterial genomes. Ann N Y Acad Sci 2012; 1267:39-44. [PMID: 22954215 DOI: 10.1111/j.1749-6632.2012.06584.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mutability as mechanism for rapid adaptation to environmental challenge is an alluringly simple concept whose apotheosis is realized in simple sequence repeats (SSR). Bacterial genomes of several species contain SSRs with a proven role in adaptation to environmental fluctuations. SSRs are hypermutable and generate reversible mutations in localized regions of bacterial genomes, leading to phase variable ON/OFF switches in gene expression. The application of genetic, bioinformatic, and mathematical/computational modeling approaches are revolutionizing our current understanding of how genomic molecular forces and environmental factors influence SSR-mediated adaptation and led to evolution of this mechanism of localized hypermutation in bacterial genomes.
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Gemayel R, Cho J, Boeynaems S, Verstrepen KJ. Beyond junk-variable tandem repeats as facilitators of rapid evolution of regulatory and coding sequences. Genes (Basel) 2012; 3:461-80. [PMID: 24704980 PMCID: PMC3899988 DOI: 10.3390/genes3030461] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 07/19/2012] [Accepted: 07/21/2012] [Indexed: 01/19/2023] Open
Abstract
Copy Number Variations (CNVs) and Single Nucleotide Polymorphisms (SNPs) have been the major focus of most large-scale comparative genomics studies to date. Here, we discuss a third, largely ignored, type of genetic variation, namely changes in tandem repeat number. Historically, tandem repeats have been designated as non functional “junk” DNA, mostly as a result of their highly unstable nature. With the exception of tandem repeats involved in human neurodegenerative diseases, repeat variation was often believed to be neutral with no phenotypic consequences. Recent studies, however, have shown that as many as 10% to 20% of coding and regulatory sequences in eukaryotes contain an unstable repeat tract. Contrary to initial suggestions, tandem repeat variation can have useful phenotypic consequences. Examples include rapid variation in microbial cell surface, tuning of internal molecular clocks in flies and the dynamic morphological plasticity in mammals. As such, tandem repeats can be useful functional elements that facilitate evolvability and rapid adaptation.
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Affiliation(s)
- Rita Gemayel
- Laboratory for Systems Biology, VIB, Gaston Geenslaan 1, B-3001 Heverlee, Belgium.
| | - Janice Cho
- Laboratory for Systems Biology, VIB, Gaston Geenslaan 1, B-3001 Heverlee, Belgium.
| | - Steven Boeynaems
- Laboratory for Systems Biology, VIB, Gaston Geenslaan 1, B-3001 Heverlee, Belgium.
| | - Kevin J Verstrepen
- Laboratory for Systems Biology, VIB, Gaston Geenslaan 1, B-3001 Heverlee, Belgium.
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47
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Gawthorne JA, Beatson SA, Srikhanta YN, Fox KL, Jennings MP. Origin of the diversity in DNA recognition domains in phasevarion associated modA genes of pathogenic Neisseria and Haemophilus influenzae. PLoS One 2012; 7:e32337. [PMID: 22457715 PMCID: PMC3311624 DOI: 10.1371/journal.pone.0032337] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Accepted: 01/26/2012] [Indexed: 02/06/2023] Open
Abstract
Phase variable restriction-modification (R-M) systems have been identified in a range of pathogenic bacteria. In some it has been demonstrated that the random switching of the mod (DNA methyltransferase) gene mediates the coordinated expression of multiple genes and constitutes a phasevarion (phase variable regulon). ModA of Neisseria and Haemophilus influenzae contain a highly variable, DNA recognition domain (DRD) that defines the target sequence that is modified by methylation and is used to define modA alleles. 18 distinct modA alleles have been identified in H. influenzae and the pathogenic Neisseria. To determine the origin of DRD variability, the 18 modA DRDs were used to search the available databases for similar sequences. Significant matches were identified between several modA alleles and mod gene from distinct bacterial species, indicating one source of the DRD variability was via horizontal gene transfer. Comparison of DRD sequences revealed significant mosaicism, indicating exchange between the Neisseria and H. influenzae modA alleles. Regions of high inter- and intra-allele similarity indicate that some modA alleles had undergone recombination more frequently than others, generating further diversity. Furthermore, the DRD from some modA alleles, such as modA12, have been transferred en bloc to replace the DRD from different modA alleles.
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Affiliation(s)
- Jayde A. Gawthorne
- Institute for Glycomics, Griffith University Gold Coast, Queensland, Australia
- Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Queensland, Australia
| | - Scott A. Beatson
- Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Queensland, Australia
| | | | - Kate L. Fox
- Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Queensland, Australia
| | - Michael P. Jennings
- Institute for Glycomics, Griffith University Gold Coast, Queensland, Australia
- * E-mail:
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Bayliss CD, Bidmos FA, Anjum A, Manchev VT, Richards RL, Grossier JP, Wooldridge KG, Ketley JM, Barrow PA, Jones MA, Tretyakov MV. Phase variable genes of Campylobacter jejuni exhibit high mutation rates and specific mutational patterns but mutability is not the major determinant of population structure during host colonization. Nucleic Acids Res 2012; 40:5876-89. [PMID: 22434884 PMCID: PMC3401435 DOI: 10.1093/nar/gks246] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Phase variation of surface structures occurs in diverse bacterial species due to stochastic, high frequency, reversible mutations. Multiple genes of Campylobacter jejuni are subject to phase variable gene expression due to mutations in polyC/G tracts. A modal length of nine repeats was detected for polyC/G tracts within C. jejuni genomes. Switching rates for these tracts were measured using chromosomally-located reporter constructs and high rates were observed for cj1139 (G8) and cj0031 (G9). Alteration of the cj1139 tract from G8 to G11 increased mutability 10-fold and changed the mutational pattern from predominantly insertions to mainly deletions. Using a multiplex PCR, major changes were detected in ‘on/off’ status for some phase variable genes during passage of C. jejuni in chickens. Utilization of observed switching rates in a stochastic, theoretical model of phase variation demonstrated links between mutability and genetic diversity but could not replicate observed population diversity. We propose that modal repeat numbers have evolved in C. jejuni genomes due to molecular drivers associated with the mutational patterns of these polyC/G repeats, rather than by selection for particular switching rates, and that factors other than mutational drift are responsible for generating genetic diversity during host colonization by this bacterial pathogen.
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Kumar P, Nagarajaram HA. A study on mutational dynamics of simple sequence repeats in relation to mismatch repair system in prokaryotic genomes. J Mol Evol 2012; 74:127-39. [PMID: 22415400 DOI: 10.1007/s00239-012-9491-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2011] [Accepted: 02/15/2012] [Indexed: 11/30/2022]
Abstract
Mutational bias toward expansion or contraction of simple sequence repeats (SSRs) is referred to as directionality of SSR evolution. In this communication, we report the mutational bias exhibited by mononucleotide SSRs occurring in the non-coding regions of several prokaryotic genomes. Our investigations revealed that the strains or species lacking mismatch repair (MMR) system generally show higher number of polymorphic SSRs than those species/strains having MMR system. An exception to this observation was seen in the mycobacterial genomes that are MMR deficient where only a few SSR tracts were seen with mutations. This low incidence of SSR mutations even in the MMR-deficient background could be attributed to the high fidelity of the DNA polymerases as a consequence of high generation time of the mycobacteria. MMR system-deficient species generally did not show any bias toward mononucleotide SSR expansions or contractions indicating a neutral evolution of SSRs in these species. The MMR-proficient species in which the observed mutations correspond to secondary mutations showed bias toward contraction of polymononucleotide tracts, perhaps, indicating low efficiency of MMR system to repair SSR-induced slippage errors on template strands. This bias toward deletion in the mononucleotide SSR tracts might be a probable reason behind scarcity for long poly A|T and G|C tracts in prokaryotic systems which are mostly MMR proficient. In conclusion, our study clearly demonstrates mutational dynamics of SSRs in relation to the presence/absence of MMR system in the prokaryotic system.
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Affiliation(s)
- Pankaj Kumar
- Laboratory of Computational Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD), Tuljaguda Complex, 4-1-714, Mozamjahi Rd, Nampally, Hyderabad, 500 001, India
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Phosphorylcholine allows for evasion of bactericidal antibody by Haemophilus influenzae. PLoS Pathog 2012; 8:e1002521. [PMID: 22396641 PMCID: PMC3291618 DOI: 10.1371/journal.ppat.1002521] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Accepted: 12/20/2011] [Indexed: 11/19/2022] Open
Abstract
The human pathogen Haemophilus influenzae has the ability to quickly adapt to different host environments through phase variation of multiple structures on its lipooligosaccharide (LPS), including phosphorylcholine (ChoP). During colonization with H. influenzae, there is a selection for ChoP+ phase variants. In a murine model of nasopharyngeal colonization, this selection is lost in the absence of adaptive immunity. Based on previous data highlighting the importance of natural antibody in limiting H. influenzae colonization, the effect of ChoP expression on antibody binding and its bactericidal activity was investigated. Flow cytometric analysis revealed that ChoP+ phase variants had decreased binding of antibody to LPS epitopes compared to ChoP- phase variants. This difference in antibody binding correlated with increased survival of ChoP+ phase variants in the presence of antibody-dependent, complement-mediated killing. ChoP+ phase variants were also more resistant to trypsin digestion, suggesting a general effect on the physical properties of the outer membrane. Moreover, ChoP-mediated protection against antibody binding correlated with increased resilience of outer membrane integrity. Collectively, these data suggest that ChoP expression provides a selective advantage during colonization through ChoP-mediated effects on the accessibility of bactericidal antibody to the cell surface.
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