1
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Motamedi H, Abiri R, Salari F, Jalili C, Alvandi A. Reduction of UreB and CagA expression level by siRNA construct in Helicobacter pylori strain SS1. BMC Microbiol 2023; 23:401. [PMID: 38114907 PMCID: PMC10729366 DOI: 10.1186/s12866-023-03143-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 12/05/2023] [Indexed: 12/21/2023] Open
Abstract
BACKGROUND Two important virulence factors, urease and cagA, play an important role in Helicobacter pylori (H. pylori) gastric cancer. Aim of this study was to investigate the expression level and function of ureB and cagA using small interfering RNAs (siRNA). METHODS SS1 strain of H. pylori was considered as host for natural transformation. siRNA designed for ureB and cagA genes were inserted in pGPU6/GFP/Neo siRNA plasmid vector to evaluate using phenotypic and genotypic approaches. Then, qPCR was performed for determining inhibition rate of ureB and cagA gene expression. RESULTS The expression levels of siRNA-ureB and siRNA-cagA in the recombinant strain SS1 were reduced by about 5000 and 1000 fold, respectively, compared to the native H. pylori strain SS1. Also, preliminary evaluation of siRNA-ureB in vitro showed inhibition of urea enzyme activity. These data suggest that siRNA may be a powerful new tool for gene silencing in vitro, and for the development of RNAi-based anti-H. pylori therapies. CONCLUSION Our results show that targeting ureB and cagA genes with siRNA seems to be a new strategy to inhibit urease enzyme activity, reduce inflammation and colonization rate.
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Affiliation(s)
- Hamid Motamedi
- Department of Microbiology, School of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
- Student Research Committee, School of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Ramin Abiri
- Fertility and Infertility Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Farhad Salari
- Department of Immunology, School of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Cyrus Jalili
- Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Amirhoushang Alvandi
- Medical Technology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran.
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2
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Förster M, Rathmann I, Yüksel M, Power JJ, Maier B. Genome-wide transformation reveals extensive exchange across closely related Bacillus species. Nucleic Acids Res 2023; 51:12352-12366. [PMID: 37971327 PMCID: PMC10711437 DOI: 10.1093/nar/gkad1074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 09/07/2023] [Accepted: 11/02/2023] [Indexed: 11/19/2023] Open
Abstract
Bacterial transformation is an important mode of horizontal gene transfer that helps spread genetic material across species boundaries. Yet, the factors that pose barriers to genome-wide cross-species gene transfer are poorly characterized. Here, we develop a replacement accumulation assay to study the effects of genomic distance on transfer dynamics. Using Bacillus subtilis as recipient and various species of the genus Bacillus as donors, we find that the rate of orthologous replacement decreases exponentially with the divergence of their core genomes. We reveal that at least 96% of the B. subtilis core genes are accessible to replacement by alleles from Bacillus spizizenii. For the more distantly related Bacillus atrophaeus, gene replacement events cluster at genomic locations with high sequence identity and preferentially replace ribosomal genes. Orthologous replacement also creates mosaic patterns between donor and recipient genomes, rearranges the genome architecture, and governs gain and loss of accessory genes. We conclude that cross-species gene transfer is dominated by orthologous replacement of core genes which occurs nearly unrestricted between closely related species. At a lower rate, the exchange of accessory genes gives rise to more complex genome dynamics.
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Affiliation(s)
- Mona Förster
- Institute for Biological Physics, University of Cologne, Zülpicherstr. 47a, 50674 Köln, Germany
| | - Isabel Rathmann
- Institute for Biological Physics, University of Cologne, Zülpicherstr. 47a, 50674 Köln, Germany
| | - Melih Yüksel
- Institute for Biological Physics, University of Cologne, Zülpicherstr. 47a, 50674 Köln, Germany
| | - Jeffrey J Power
- Institute for Biological Physics, University of Cologne, Zülpicherstr. 47a, 50674 Köln, Germany
| | - Berenike Maier
- Institute for Biological Physics, University of Cologne, Zülpicherstr. 47a, 50674 Köln, Germany
- Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
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3
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Noszka M, Strzałka A, Muraszko J, Kolenda R, Meng C, Ludwig C, Stingl K, Zawilak-Pawlik A. Profiling of the Helicobacter pylori redox switch HP1021 regulon using a multi-omics approach. Nat Commun 2023; 14:6715. [PMID: 37872172 PMCID: PMC10593804 DOI: 10.1038/s41467-023-42364-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 10/09/2023] [Indexed: 10/25/2023] Open
Abstract
The gastric human pathogen Helicobacter pylori has developed mechanisms to combat stress factors, including reactive oxygen species (ROS). Here, we present a comprehensive study on the redox switch protein HP1021 regulon combining transcriptomic, proteomic and DNA-protein interactions analyses. Our results indicate that HP1021 modulates H. pylori's response to oxidative stress. HP1021 controls the transcription of 497 genes, including 407 genes related to response to oxidative stress. 79 proteins are differently expressed in the HP1021 deletion mutant. HP1021 controls typical ROS response pathways (katA, rocF) and less canonical ones, particularly DNA uptake and central carbohydrate metabolism. HP1021 is a molecular regulator of competence in H. pylori, as HP1021-dependent repression of the comB DNA uptake genes is relieved under oxidative conditions, increasing natural competence. Furthermore, HP1021 controls glucose consumption by directly regulating the gluP transporter and has an important impact on maintaining the energetic balance in the cell.
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Affiliation(s)
- Mateusz Noszka
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland
| | - Agnieszka Strzałka
- Department of Molecular Microbiology, Faculty of Biotechnology, University of Wrocław, Wrocław, Poland
| | - Jakub Muraszko
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland
| | - Rafał Kolenda
- Department of Biochemistry and Molecular Biology, Wrocław University of Environmental and Life Sciences, Wrocław, Poland
- Quadram Institute Biosciences, Norwich Research Park, Norwich, UK
| | - Chen Meng
- Bavarian Center for Biomolecular Mass Spectrometry (BayBioMS), Technical University of Munich (TUM), Freising, Germany
| | - Christina Ludwig
- Bavarian Center for Biomolecular Mass Spectrometry (BayBioMS), Technical University of Munich (TUM), Freising, Germany
| | - Kerstin Stingl
- Department of Biological Safety, National Reference Laboratory for Campylobacter, German Federal Institute for Risk Assessment, Berlin, Germany
| | - Anna Zawilak-Pawlik
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland.
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4
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Calderón-Franco D, van Loosdrecht MCM, Abeel T, Weissbrodt DG. Catch me if you can: capturing microbial community transformation by extracellular DNA using Hi-C sequencing. Antonie Van Leeuwenhoek 2023:10.1007/s10482-023-01834-z. [PMID: 37156983 DOI: 10.1007/s10482-023-01834-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 04/24/2023] [Indexed: 05/10/2023]
Abstract
The transformation of environmental microorganisms by extracellular DNA is an overlooked mechanism of horizontal gene transfer and evolution. It initiates the acquisition of exogenous genes and propagates antimicrobial resistance alongside vertical and conjugative transfers. We combined mixed-culture biotechnology and Hi-C sequencing to elucidate the transformation of wastewater microorganisms with a synthetic plasmid encoding GFP and kanamycin resistance genes, in the mixed culture of chemostats exposed to kanamycin at concentrations representing wastewater, gut and polluted environments (0.01-2.5-50-100 mg L-1). We found that the phylogenetically distant Gram-negative Runella (102 Hi-C links), Bosea (35), Gemmobacter (33) and Zoogloea (24) spp., and Gram-positive Microbacterium sp. (90) were transformed by the foreign plasmid, under high antibiotic exposure (50 mg L-1). In addition, the antibiotic pressure shifted the origin of aminoglycoside resistance genes from genomic DNA to mobile genetic elements on plasmids accumulating in microorganisms. These results reveal the power of Hi-C sequencing to catch and surveil the transfer of xenogenetic elements inside microbiomes.
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Affiliation(s)
| | | | - Thomas Abeel
- Delft Bioinformatics Lab, Delft University of Technology, Delft, The Netherlands
- Infectious Disease and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - David G Weissbrodt
- Department of Biotechnology, Delft University of Technology, Delft, The Netherlands.
- Department of Biotechnology and Food Science, Norwegian University of Science and Technology, Trondheim, Norway.
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5
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The Helicobacter pylori UvrC Nuclease Is Essential for Chromosomal Microimports after Natural Transformation. mBio 2022; 13:e0181122. [PMID: 35876509 PMCID: PMC9426483 DOI: 10.1128/mbio.01811-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Helicobacter pylori is a Gram-negative bacterial carcinogenic pathogen that infects the stomachs of half of the human population. It is a natural mutator due to a deficient DNA mismatch repair pathway and is naturally competent for transformation. As a result, it is one of the most genetically diverse human bacterial pathogens. The length of chromosomal imports in H. pylori follows an unusual bimodal distribution consisting of macroimports with a mean length of 1,645 bp and microimports with a mean length of 28 bp. The mechanisms responsible for this import pattern were unknown. Here, we used a high-throughput whole-genome transformation assay to elucidate the role of nucleotide excision repair pathway (NER) components on import length distribution. The data show that the integration of microimports depended on the activity of the UvrC endonuclease, while none of the other components of the NER pathway was required. Using H. pylori site-directed mutants, we showed that the widely conserved UvrC nuclease active sites, while essential for protection from UV light, one of the canonical NER functions, are not required for generation of microimports. A quantitative analysis of recombination patterns based on over 1,000 imports from over 200 sequenced recombinant genomes showed that microimports occur frequently within clusters of multiple imports, strongly suggesting they derive from a single strand invasion event. We propose a hypothetical model of homologous recombination in H. pylori, involving a novel function of UvrC, that reconciles the available experimental data about recombination patterns in H. pylori. IMPORTANCE Helicobacter pylori is one of the most common and genetically diverse human bacterial pathogens. It is responsible for chronic gastritis and represents the main risk factor for gastric cancer. In H. pylori, DNA fragments can be imported by recombination during natural transformation. The length of those fragments determines how many potentially beneficial or deleterious alleles are acquired and thus influences adaptation to the gastric niche. Here, we used a transformation assay to examine imported fragments across the chromosome. We show that UvrC, an endonuclease involved in DNA repair, is responsible for the specific integration of short DNA fragments. This suggests that short and long fragments are imported through distinct recombination pathways. We also show that short fragments are frequently clustered with longer fragments, suggesting that both pathways may be mechanistically linked. These findings provide a novel basis to explain how H. pylori can fine-tune the genetic diversity acquired by transformation.
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6
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Recombination resolves the cost of horizontal gene transfer in experimental populations of Helicobacter pylori. Proc Natl Acad Sci U S A 2022; 119:e2119010119. [PMID: 35298339 PMCID: PMC8944584 DOI: 10.1073/pnas.2119010119] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Horizontal gene transfer (HGT)—the transfer of DNA between lineages—is responsible for a large proportion of the genetic variation that contributes to evolution in microbial populations. While HGT can bring beneficial genetic innovation, the transfer of DNA from other species or strains can also have deleterious effects. In this study, we evolve populations of the bacteria Helicobacter pylori and use DNA sequencing to identify over 40,000 genetic variants transferred by HGT. We measure the cost of many of these and find that both strongly beneficial mutations and deleterious mutations are genetic variants transferred by natural transformation. Importantly, we also show how recombination that separates linked beneficial and deleterious mutations resolves the cost of HGT. Horizontal gene transfer (HGT) is important for microbial evolution, yet we know little about the fitness effects and dynamics of horizontally transferred genetic variants. In this study, we evolve laboratory populations of Helicobacter pylori, which take up DNA from their environment by natural transformation, and measure the fitness effects of thousands of transferred genetic variants. We find that natural transformation increases the rate of adaptation but comes at the cost of significant genetic load. We show that this cost is circumvented by recombination, which increases the efficiency of selection by decoupling deleterious and beneficial genetic variants. Our results show that adaptation with HGT, pervasive in natural microbial populations, is shaped by a combination of selection, recombination, and genetic drift not accounted for in existing models of evolution.
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7
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Ailloud F, Estibariz I, Suerbaum S. Evolved to vary: genome and epigenome variation in the human pathogen Helicobacter pylori. FEMS Microbiol Rev 2021; 45:5900976. [PMID: 32880636 DOI: 10.1093/femsre/fuaa042] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 08/31/2020] [Indexed: 12/24/2022] Open
Abstract
Helicobacter pylori is a Gram-negative, spiral shaped bacterium that selectively and chronically infects the gastric mucosa of humans. The clinical course of this infection can range from lifelong asymptomatic infection to severe disease, including peptic ulcers or gastric cancer. The high mutation rate and natural competence typical of this species are responsible for massive inter-strain genetic variation exceeding that observed in all other bacterial human pathogens. The adaptive value of such a plastic genome is thought to derive from a rapid exploration of the fitness landscape resulting in fast adaptation to the changing conditions of the gastric environment. Nevertheless, diversity is also lost through recurrent bottlenecks and H. pylori's lifestyle is thus a perpetual race to maintain an appropriate pool of standing genetic variation able to withstand selection events. Another aspect of H. pylori's diversity is a large and variable repertoire of restriction-modification systems. While not yet completely understood, methylome evolution could generate enough transcriptomic variation to provide another intricate layer of adaptive potential. This review provides an up to date synopsis of this rapidly emerging area of H. pylori research that has been enabled by the ever-increasing throughput of Omics technologies and a multitude of other technological advances.
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Affiliation(s)
- Florent Ailloud
- Max von Pettenkofer Institute, Faculty of Medicine, LMU München, Pettenkoferstr. 9a, 80336 München, Germany
| | - Iratxe Estibariz
- Max von Pettenkofer Institute, Faculty of Medicine, LMU München, Pettenkoferstr. 9a, 80336 München, Germany
| | - Sebastian Suerbaum
- Max von Pettenkofer Institute, Faculty of Medicine, LMU München, Pettenkoferstr. 9a, 80336 München, Germany.,DZIF Deutsches Zentrum für Infektionsforschung, Partner Site Munich, Pettenkoferstr. 9a, 80336 München, Germany.,National Reference Center for Helicobacter pylori, Pettenkoferstr. 9a, 80336 München, Germany
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8
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Nkuize M, Vanderpas J, Buset M, Gomez-Galdon M, Delforge M, Miendje-Deyi VY, Muls V, De Wit S. Primary antibiotic resistance of Helicobacter pylori isolates is twofold more frequent in HIV-positive than HIV-negative individuals: A descriptive observational study. Microbiologyopen 2021; 10:e1184. [PMID: 34180600 PMCID: PMC8166256 DOI: 10.1002/mbo3.1184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 03/05/2021] [Accepted: 03/23/2021] [Indexed: 11/11/2022] Open
Abstract
The antimicrobial susceptibility of Helicobacter pylori strains isolated from HIV-positive individuals is not well characterized. This study aimed to measure the prevalence and long-term trends associated with primary H. pylori antibiotic resistance, evaluate correlations with antibiotic consumption, and compare predictors for H. pylori antibiotic resistance between HIV-positive and HIV-negative individuals. In this longitudinal registry study, we evaluated consecutive adults with and without HIV infection, naïve to H. pylori treatment, who underwent upper gastrointestinal endoscopy and had a positive H. pylori culture, with susceptibility testing available, between 2004 and 2015. Outpatient antibiotic consumption data were based on nationwide aggregated numbers. H. pylori was isolated from gastric biopsies of 3008/8321 patients, 181/477 (37.9%) were HIV-positive and 2827/7844 (36.0%) HIV-negative. Overall cohort mean prevalence of H. pylori primary antibiotic resistance was 11.1% for clarithromycin, 17.8% levofloxacin, and 39.4% metronidazole. The prevalence of H. pylori primary resistance was significantly higher for these three drugs in HIV-positive individuals across the study period. Linear regression showed that the prevalence of clarithromycin and levofloxacin resistance correlated with the country aggregate daily dose consumption of macrolides and quinolones, respectively. Multivariable regression analysis showed that HIV infection is a strong independent risk factor for multiple H. pylori antibiotic resistance. In summary, HIV infection is a risk factor for carrying multi-resistant H. pylori strains and this is correlated with antibiotic consumption. Empirical therapies should be avoided in HIV-positive individuals. These data highlight the need to implement ongoing monitoring of H. pylori antimicrobial susceptibility among HIV-positive individuals. The study is registered at ISRCTN registry, number 13466428: https://www.isrctn.com/ISRCTN13466428.
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Affiliation(s)
- Marcel Nkuize
- Department of Gastroenterology and Hepatology, CHU Saint Pierre Université Libre de Bruxelles, Bruxelles, Belgium
| | - Jean Vanderpas
- Department of Hospital Hygiene & Infection Control, CHU Saint Pierre Université Libre de Bruxelles, Bruxelles, Belgium
| | - Michel Buset
- Department of Gastroenterology and Hepatology, CHU Saint Pierre Université Libre de Bruxelles, Bruxelles, Belgium.,Department of Gastroenterology and Hepatology, Delta Hospital, CHIREC, Bruxelles, Belgium
| | - Maria Gomez-Galdon
- Department of Pathology, Institut Jules Bordet, Université Libre de Bruxelles, Bruxelles, Belgium
| | - Marc Delforge
- Department of Infectious Diseases, CHU Saint Pierre Université Libre de Bruxelles, Bruxelles, Belgium
| | - Véronique Yvette Miendje-Deyi
- Department of Microbiology-LHUB, Pôle Hospitalier Universitaire de Bruxelles, Université Libre de Bruxelles, Bruxelles, Belgium
| | - Vinciane Muls
- Department of Gastroenterology and Hepatology, CHU Saint Pierre Université Libre de Bruxelles, Bruxelles, Belgium
| | - Stéphane De Wit
- Department of Infectious Diseases, CHU Saint Pierre Université Libre de Bruxelles, Bruxelles, Belgium
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9
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Slomka S, Françoise I, Hornung G, Asraf O, Biniashvili T, Pilpel Y, Dahan O. Experimental Evolution of Bacillus subtilis Reveals the Evolutionary Dynamics of Horizontal Gene Transfer and Suggests Adaptive and Neutral Effects. Genetics 2020; 216:543-558. [PMID: 32847815 PMCID: PMC7536860 DOI: 10.1534/genetics.120.303401] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 08/16/2020] [Indexed: 12/18/2022] Open
Abstract
Tracing evolutionary processes that lead to fixation of genomic variation in wild bacterial populations is a prime challenge in molecular evolution. In particular, the relative contribution of horizontal gene transfer (HGT) vs.de novo mutations during adaptation to a new environment is poorly understood. To gain a better understanding of the dynamics of HGT and its effect on adaptation, we subjected several populations of competent Bacillus subtilis to a serial dilution evolution on a high-salt-containing medium, either with or without foreign DNA from diverse pre-adapted or naturally salt tolerant species. Following 504 generations of evolution, all populations improved growth yield on the medium. Sequencing of evolved populations revealed extensive acquisition of foreign DNA from close Bacillus donors but not from more remote donors. HGT occurred in bursts, whereby a single bacterial cell appears to have acquired dozens of fragments at once. In the largest burst, close to 2% of the genome has been replaced by HGT. Acquired segments tend to be clustered in integration hotspots. Other than HGT, genomes also acquired spontaneous mutations. Many of these mutations occurred within, and seem to alter, the sequence of flagellar proteins. Finally, we show that, while some HGT fragments could be neutral, others are adaptive and accelerate evolution.
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Affiliation(s)
- Shai Slomka
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Itamar Françoise
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Gil Hornung
- The Nancy and Stephen Grand Israel National Center for Personalized Medicine, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Omer Asraf
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Tammy Biniashvili
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yitzhak Pilpel
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Orna Dahan
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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10
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The Patchy Distribution of Restriction⁻Modification System Genes and the Conservation of Orphan Methyltransferases in Halobacteria. Genes (Basel) 2019; 10:genes10030233. [PMID: 30893937 PMCID: PMC6471742 DOI: 10.3390/genes10030233] [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: 02/15/2019] [Revised: 03/13/2019] [Accepted: 03/14/2019] [Indexed: 12/26/2022] Open
Abstract
Restriction⁻modification (RM) systems in bacteria are implicated in multiple biological roles ranging from defense against parasitic genetic elements, to selfish addiction cassettes, and barriers to gene transfer and lineage homogenization. In bacteria, DNA-methylation without cognate restriction also plays important roles in DNA replication, mismatch repair, protein expression, and in biasing DNA uptake. Little is known about archaeal RM systems and DNA methylation. To elucidate further understanding for the role of RM systems and DNA methylation in Archaea, we undertook a survey of the presence of RM system genes and related genes, including orphan DNA methylases, in the halophilic archaeal class Halobacteria. Our results reveal that some orphan DNA methyltransferase genes were highly conserved among lineages indicating an important functional constraint, whereas RM systems demonstrated patchy patterns of presence and absence. This irregular distribution is due to frequent horizontal gene transfer and gene loss, a finding suggesting that the evolution and life cycle of RM systems may be best described as that of a selfish genetic element. A putative target motif (CTAG) of one of the orphan methylases was underrepresented in all of the analyzed genomes, whereas another motif (GATC) was overrepresented in most of the haloarchaeal genomes, particularly in those that encoded the cognate orphan methylase.
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11
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Chattopadhyay S, Chi PB, Minin VN, Berg DE, Sokurenko EV. Recombination-independent rapid convergent evolution of the gastric pathogen Helicobacter pylori. BMC Genomics 2018; 19:835. [PMID: 30463511 PMCID: PMC6249973 DOI: 10.1186/s12864-018-5231-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2018] [Accepted: 11/07/2018] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Helicobacter pylori is a human stomach pathogen, naturally-competent for DNA uptake, and prone to homologous recombination. Extensive homoplasy (i.e., phylogenetically-unlinked identical variations) observed in H. pylori genes is considered a hallmark of such recombination. However, H. pylori also exhibits a high mutation rate. The relative adaptive role of homologous recombination and mutation in species diversity is a highly-debated issue in biology. Recombination results in homoplasy. While convergent mutation can also account for homoplasy, its contribution is thought to be minor. We demonstrate here that, contrary to dogma, convergent mutation is a key contributor to Helicobacter pylori homoplasy, potentially driven by adaptive evolution of proteins. RESULTS Our present genome-wide analysis shows that homoplastic nonsynonymous (amino acid replacement) changes are not typically accompanied by homoplastic synonymous (silent) variations. Moreover, the majority of the codon positions with homoplastic nonsynonymous changes also contain different (i.e. non-homoplastic) nonsynonymous changes arising from mutation only. This indicates that, to a considerable extent, nonsynonymous homoplasy is due to convergent mutations. High mutation rate or limited availability of evolvable sites cannot explain this excessive convergence, as suggested by our simulation studies. Rather, the genes with convergent mutations are overrepresented in distinct functional categories, suggesting possible selective responses to conditions such as distinct micro-niches in single hosts, and to differences in host genotype, physiology, habitat and diet. CONCLUSIONS We propose that mutational convergence is a key player in H. pylori's adaptation and extraordinary persistence in human hosts. High frequency of mutational convergence could be due to saturation of evolvable sites capable of responding to selection pressures, while the number of mutable residues is far from saturation. We anticipate a similar scenario of mutational vs. recombinational genome dynamics or plasticity for other naturally competent microbes where strong positive selection could favor frequent convergent mutations in adaptive protein evolution.
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Affiliation(s)
| | - Peter B Chi
- Department of Mathematics and Statistics, Villanova University, Villanova, PA, USA
| | - Vladimir N Minin
- Department of Statistics, University of California, Irvine, California, USA
| | - Douglas E Berg
- Division of Infectious Diseases, Department of Medicine, University of California, San Diego, La Jolla, California, USA
| | - Evgeni V Sokurenko
- Department of Microbiology, University of Washington, Seattle, Washington, USA
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12
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Alfsnes K, Frye SA, Eriksson J, Eldholm V, Brynildsrud OB, Bohlin J, Harrison OB, Hood DW, Maiden MCJ, Tønjum T, Ambur OH. A genomic view of experimental intraspecies and interspecies transformation of a rifampicin-resistance allele into Neisseria meningitidis. Microb Genom 2018; 4. [PMID: 30251949 PMCID: PMC6321871 DOI: 10.1099/mgen.0.000222] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The spread of antibiotic resistance within and between different bacterial populations is a major health problem on a global scale. The identification of genetic transformation in genomic data from Neisseria meningitidis, the meningococcus (Mc), and other bacteria is problematic, since similar or even identical alleles may be involved. A particular challenge in naturally transformable bacteria generally is to distinguish between common ancestry and true recombined sites in sampled genome sequences. Furthermore, the identification of recombination following experimental transformation of homologous alleles requires identifiable differences between donor and recipient, which in itself influences the propensity for homologous recombination (HR). This study identifies the distribution of HR events following intraspecies and interspecies Mc transformations of rpoB alleles encoding rifampicin resistance by whole-genome DNA sequencing and single nucleotide variant analysis. The HR events analysed were confined to the genomic region surrounding the single nucleotide genetic marker used for selection. An exponential length distribution of these recombined events was found, ranging from a few nucleotides to about 72 kb stretches. The lengths of imported sequences were on average found to be longer following experimental transformation of the recipient with genomic DNA from an intraspecies versus an interspecies donor (P<0.001). The recombination events were generally observed to be mosaic, with donor sequences interspersed with recipient sequence. Here, we present four models to explain these observations, by fragmentation of the transformed DNA, by interruptions of the recombination mechanism, by secondary recombination of endogenous self-DNA, or by repair/replication mechanisms.
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Affiliation(s)
| | - Stephan A Frye
- 2Department of Microbiology, Oslo University Hospital (Rikshospitalet), Oslo, Norway
| | - Jens Eriksson
- 2Department of Microbiology, Oslo University Hospital (Rikshospitalet), Oslo, Norway
| | - Vegard Eldholm
- 3Department of Molecular Biology, Domain of Infection Control and Environmental Health, Norwegian Institute of Public Health, Oslo, Norway
| | - Ola Brønstad Brynildsrud
- 4Department of Methodology Research and Analysis, Domain of Infection Control and Environmental Health, Norwegian Institute of Public Health, Oslo, Norway
| | - Jon Bohlin
- 4Department of Methodology Research and Analysis, Domain of Infection Control and Environmental Health, Norwegian Institute of Public Health, Oslo, Norway
| | - Odile B Harrison
- 5The Peter Medawar Building for Pathogen Research, University of Oxford, Oxford, UK
| | - Derek W Hood
- 6Nuffield Department of Clinical Medicine, University of Oxford, John Radcliffe Hospital, Headington, Oxford, UK
| | - Martin C J Maiden
- 5The Peter Medawar Building for Pathogen Research, University of Oxford, Oxford, UK
| | - Tone Tønjum
- 2Department of Microbiology, Oslo University Hospital (Rikshospitalet), Oslo, Norway.,7Department of Microbiology, University of Oslo, Oslo, Norway
| | - Ole Herman Ambur
- 2Department of Microbiology, Oslo University Hospital (Rikshospitalet), Oslo, Norway.,8OsloMet - Oslo Metropolitan University, Oslo, Norway
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13
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Cowley LA, Petersen FC, Junges R, Jimson D. Jimenez M, Morrison DA, Hanage WP. Evolution via recombination: Cell-to-cell contact facilitates larger recombination events in Streptococcus pneumoniae. PLoS Genet 2018; 14:e1007410. [PMID: 29897968 PMCID: PMC6016952 DOI: 10.1371/journal.pgen.1007410] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 06/25/2018] [Accepted: 05/11/2018] [Indexed: 12/16/2022] Open
Abstract
Homologous recombination in the genetic transformation model organism Streptococcus pneumoniae is thought to be important in the adaptation and evolution of this pathogen. While competent pneumococci are able to scavenge DNA added to laboratory cultures, large-scale transfers of multiple kb are rare under these conditions. We used whole genome sequencing (WGS) to map transfers in recombinants arising from contact of competent cells with non-competent ‘target’ cells, using strains with known genomes, distinguished by a total of ~16,000 SNPs. Experiments designed to explore the effect of environment on large scale recombination events used saturating purified donor DNA, short-term cell assemblages on Millipore filters, and mature biofilm mixed cultures. WGS of 22 recombinants for each environment mapped all SNPs that were identical between the recombinant and the donor but not the recipient. The mean recombination event size was found to be significantly larger in cell-to-cell contact cultures (4051 bp in filter assemblage and 3938 bp in biofilm co-culture versus 1815 bp with saturating DNA). Up to 5.8% of the genome was transferred, through 20 recombination events, to a single recipient, with the largest single event incorporating 29,971 bp. We also found that some recombination events are clustered, that these clusters are more likely to occur in cell-to-cell contact environments, and that they cause significantly increased linkage of genes as far apart as 60,000 bp. We conclude that pneumococcal evolution through homologous recombination is more likely to occur on a larger scale in environments that permit cell-to-cell contact. Bacteria shuffle their genes far less often than humans do and genes or traits are more directly linked with the singular bacterial parent cell rather than the two parents that are involved in sexual reproduction. However, bacteria do occasionally have sex in the form of homologous recombination by taking up external DNA and incorporating it into their genomes. This happens far less regularly than sexual reproduction happens in human generations but is a known way that bacteria undergo ‘Horizontal gene transfer’. This means that genes can be acquired without being inherited. In this study we show that this form of horizontal gene transfer is more likely to happen in certain environments over others in Streptococcus pneumoniae. In particular, we show that this is more likely to happen in environments that closely mirror the nasopharynx which is the natural habitat of S. pneumoniae.
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Affiliation(s)
- Lauren A. Cowley
- Department of Epidemiology, Harvard TH Chan School of Public Health, Boston, United States of America
- * E-mail:
| | | | - Roger Junges
- Department of Oral Biology, University of Oslo, Oslo, Norway
| | - Med Jimson D. Jimenez
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, United States of America
| | - Donald A. Morrison
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, United States of America
| | - William P. Hanage
- Department of Epidemiology, Harvard TH Chan School of Public Health, Boston, United States of America
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14
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Akita T, Takuno S, Innan H. Coalescent framework for prokaryotes undergoing interspecific homologous recombination. Heredity (Edinb) 2018; 120:474-484. [PMID: 29358726 PMCID: PMC5889408 DOI: 10.1038/s41437-017-0034-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Revised: 10/04/2017] [Accepted: 10/23/2017] [Indexed: 12/11/2022] Open
Abstract
Coalescent process for prokaryote species is theoretically considered. Prokaryotes undergo homologous recombination with individuals of the same species (intraspecific recombination) and with individuals of other species (interspecific recombination). This work particularly focuses on interspecific recombination because intraspecific recombination has been well incorporated in coalescent framework. We present a simulation framework for generating SNP (single-nucleotide polymorphism) patterns that allows external DNA integration into host genome from other species. Using this simulation tool, msPro, we observed that the joint processes of intra- and interspecific recombination generate complex SNP patterns. The direct effect of interspecific recombination includes increased polymorphism. Because interspecific recombination is very rare in nature, it generates regions with exceptionally high polymorphism. Following interspecific recombination, intraspecific recombination cuts the integrated external DNA into small fragments, generating a complex SNP pattern that appears as if external DNA was integrated multiple times. The insight gained from our work using the msPro simulator will be useful for understanding and evaluating the relative contributions of intra- and interspecific recombination events in generating complex SNP patters in prokaryotes.
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Affiliation(s)
- Tetsuya Akita
- Graduate University for Advanced Studies, Hayama, Kanagawa, 240-0193, Japan
- National Research Institute of Far Seas Fisheries, Fisheries Research Agency, Yokohama, Kanagawa, 236-8648, Japan
| | - Shohei Takuno
- Graduate University for Advanced Studies, Hayama, Kanagawa, 240-0193, Japan
| | - Hideki Innan
- Graduate University for Advanced Studies, Hayama, Kanagawa, 240-0193, Japan.
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15
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Ouellette M, Gogarten JP, Lajoie J, Makkay AM, Papke RT. Characterizing the DNA Methyltransferases of Haloferax volcanii via Bioinformatics, Gene Deletion, and SMRT Sequencing. Genes (Basel) 2018; 9:genes9030129. [PMID: 29495512 PMCID: PMC5867850 DOI: 10.3390/genes9030129] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 02/16/2018] [Accepted: 02/19/2018] [Indexed: 12/31/2022] Open
Abstract
DNA methyltransferases (MTases), which catalyze the methylation of adenine and cytosine bases in DNA, can occur in bacteria and archaea alongside cognate restriction endonucleases (REases) in restriction-modification (RM) systems or independently as orphan MTases. Although DNA methylation and MTases have been well-characterized in bacteria, research into archaeal MTases has been limited. A previous study examined the genomic DNA methylation patterns (methylome) of the halophilic archaeon Haloferax volcanii, a model archaeal system which can be easily manipulated in laboratory settings, via single-molecule real-time (SMRT) sequencing and deletion of a putative MTase gene (HVO_A0006). In this follow-up study, we deleted other putative MTase genes in H. volcanii and sequenced the methylomes of the resulting deletion mutants via SMRT sequencing to characterize the genes responsible for DNA methylation. The results indicate that deletion of putative RM genes HVO_0794, HVO_A0006, and HVO_A0237 in a single strain abolished methylation of the sole cytosine motif in the genome (Cm4TAG). Amino acid alignments demonstrated that HVO_0794 shares homology with characterized cytosine CTAG MTases in other organisms, indicating that this MTase is responsible for Cm4TAG methylation in H. volcanii. The CTAG motif has high density at only one of the origins of replication, and there is no relative increase in CTAG motif frequency in the genome of H. volcanii, indicating that CTAG methylation might not have effectively taken over the role of regulating DNA replication and mismatch repair in the organism as previously predicted. Deletion of the putative Type I RM operon rmeRMS (HVO_2269-2271) resulted in abolished methylation of the adenine motif in the genome (GCAm6BN₆VTGC). Alignments of the MTase (HVO_2270) and site specificity subunit (HVO_2271) demonstrate homology with other characterized Type I MTases and site specificity subunits, indicating that the rmeRMS operon is responsible for adenine methylation in H. volcanii. Together with HVO_0794, these genes appear to be responsible for all detected methylation in H. volcanii, even though other putative MTases (HVO_C0040, HVO_A0079) share homology with characterized MTases in other organisms. We also report the construction of a multi-RM deletion mutant (ΔRM), with multiple RM genes deleted and with no methylation detected via SMRT sequencing, which we anticipate will be useful for future studies on DNA methylation in H. volcanii.
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Affiliation(s)
- Matthew Ouellette
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06268, USA.
| | - J Peter Gogarten
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06268, USA.
| | - Jessica Lajoie
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06268, USA.
| | - Andrea M Makkay
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06268, USA.
| | - R Thane Papke
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06268, USA.
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16
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Maddamsetti R, Lenski RE. Analysis of bacterial genomes from an evolution experiment with horizontal gene transfer shows that recombination can sometimes overwhelm selection. PLoS Genet 2018; 14:e1007199. [PMID: 29385126 PMCID: PMC5809092 DOI: 10.1371/journal.pgen.1007199] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 02/12/2018] [Accepted: 01/15/2018] [Indexed: 12/23/2022] Open
Abstract
Few experimental studies have examined the role that sexual recombination plays in bacterial evolution, including the effects of horizontal gene transfer on genome structure. To address this limitation, we analyzed genomes from an experiment in which Escherichia coli K-12 Hfr (high frequency recombination) donors were periodically introduced into 12 evolving populations of E. coli B and allowed to conjugate repeatedly over the course of 1000 generations. Previous analyses of the evolved strains from this experiment showed that recombination did not accelerate adaptation, despite increasing genetic variation relative to asexual controls. However, the resolution in that previous work was limited to only a few genetic markers. We sought to clarify and understand these puzzling results by sequencing complete genomes from each population. The effects of recombination were highly variable: one lineage was mostly derived from the donors, while another acquired almost no donor DNA. In most lineages, some regions showed repeated introgression and others almost none. Regions with high introgression tended to be near the donors' origin of transfer sites. To determine whether introgressed alleles imposed a genetic load, we extended the experiment for 200 generations without recombination and sequenced whole-population samples. Beneficial alleles in the recipient populations were occasionally driven extinct by maladaptive donor-derived alleles. On balance, our analyses indicate that the plasmid-mediated recombination was sufficiently frequent to drive donor alleles to fixation without providing much, if any, selective advantage.
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Affiliation(s)
- Rohan Maddamsetti
- Ecology, Evolutionary Biology, and Behavior Program, Michigan State University, East Lansing, MI, United States of America
- BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, MI, United States of America
- Department of Systems Biology, Harvard Medical School, Boston, MA, United States of America
| | - Richard E. Lenski
- Ecology, Evolutionary Biology, and Behavior Program, Michigan State University, East Lansing, MI, United States of America
- BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, MI, United States of America
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, United States of America
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17
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Ilinsky Y, Kosterin OE. Molecular diversity of Wolbachia in Lepidoptera: Prevalent allelic content and high recombination of MLST genes. Mol Phylogenet Evol 2017; 109:164-179. [PMID: 28082006 DOI: 10.1016/j.ympev.2016.12.034] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Revised: 12/07/2016] [Accepted: 12/28/2016] [Indexed: 11/30/2022]
Abstract
Wolbachia are common endosymbiotic bacteria of Arthropoda and Nematoda that are ordinarily transmitted vertically in host lineages through the egg cytoplasm. Despite the great interest in the Wolbachia symbiont, many issues of its biology remain unclear, including its evolutionary history, routes of transfer among species, and the molecular mechanisms underlying the symbiont's effect on its host. In this report, we present data relating to Wolbachia infection in 120 species of 13 Lepidoptera families, mostly butterflies, from West Siberian localities based on Multilocus sequence typing (MLST) and the wsp locus and perform a comprehensive survey of the distribution of Wolbachia and its genetic diversity in Lepidoptera worldwide. We observed a high infection incidence in the studied region; this finding is probably also true for other temperate latitude regions because many studied species have broad Palearctic and even Holarctic distribution. Although 40 new MLST alleles and 31 new STs were described, there was no noticeable difference in the MLST allele content in butterflies and probably also in moths worldwide. A genetic analysis of Wolbachia strains revealed the MLST allele core in lepidopteran hosts worldwide, viz. the ST-41 allele content. The key finding of our study was the detection of rampant recombination among MLST haplotypes. High rates of homologous recombination between Wolbachia strains indicate a substantial contribution of genetic exchanges to the generation of new STs. This finding should be considered when discussing issues related to the reconstruction of Wolbachia evolution, divergence time, and the routes of Wolbachia transmission across arthropod hosts.
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Affiliation(s)
- Yury Ilinsky
- Institute of Cytology and Genetics, Russian Academy of Sciences, Siberian Branch, Novosibirsk 630090, Russia; Novosibirsk State University, Novosibirsk 630090, Russia; Institute of Chemistry and Biology, Immanuel Kant Baltic Federal University, Kaliningrad 236041, Russia.
| | - Oleg E Kosterin
- Institute of Cytology and Genetics, Russian Academy of Sciences, Siberian Branch, Novosibirsk 630090, Russia; Novosibirsk State University, Novosibirsk 630090, Russia
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18
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Clusterflock: a flocking algorithm for isolating congruent phylogenomic datasets. Gigascience 2016; 5:44. [PMID: 27776538 PMCID: PMC5078944 DOI: 10.1186/s13742-016-0152-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 10/12/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Collective animal behavior, such as the flocking of birds or the shoaling of fish, has inspired a class of algorithms designed to optimize distance-based clusters in various applications, including document analysis and DNA microarrays. In a flocking model, individual agents respond only to their immediate environment and move according to a few simple rules. After several iterations the agents self-organize, and clusters emerge without the need for partitional seeds. In addition to its unsupervised nature, flocking offers several computational advantages, including the potential to reduce the number of required comparisons. FINDINGS In the tool presented here, Clusterflock, we have implemented a flocking algorithm designed to locate groups (flocks) of orthologous gene families (OGFs) that share an evolutionary history. Pairwise distances that measure phylogenetic incongruence between OGFs guide flock formation. We tested this approach on several simulated datasets by varying the number of underlying topologies, the proportion of missing data, and evolutionary rates, and show that in datasets containing high levels of missing data and rate heterogeneity, Clusterflock outperforms other well-established clustering techniques. We also verified its utility on a known, large-scale recombination event in Staphylococcus aureus. By isolating sets of OGFs with divergent phylogenetic signals, we were able to pinpoint the recombined region without forcing a pre-determined number of groupings or defining a pre-determined incongruence threshold. CONCLUSIONS Clusterflock is an open-source tool that can be used to discover horizontally transferred genes, recombined areas of chromosomes, and the phylogenetic 'core' of a genome. Although we used it here in an evolutionary context, it is generalizable to any clustering problem. Users can write extensions to calculate any distance metric on the unit interval, and can use these distances to 'flock' any type of data.
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19
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Kojima KK, Furuta Y, Yahara K, Fukuyo M, Shiwa Y, Nishiumi S, Yoshida M, Azuma T, Yoshikawa H, Kobayashi I. Population Evolution of Helicobacter pylori through Diversification in DNA Methylation and Interstrain Sequence Homogenization. Mol Biol Evol 2016; 33:2848-2859. [PMID: 27604221 DOI: 10.1093/molbev/msw162] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Decoding of closely related genomes is now revealing the process of population evolution. In bacteria, population divergence appears associated with a unique set of sequence-specific epigenetic DNA methylation systems, often within restriction-modification (RM) systems. They might define a unique gene expression pattern and limit genetic flux between lineages in population divergence. We addressed the contribution of methylation systems to population diversification in panmictic bacterial species, Helicobacter pylori, which shows an interconnected population structure through frequent mutual recombination. We analyzed complete genome sequences of 28 strains collected in Fukui, Japan. Their nucleotide sequences are closely related although fine-scale analyses revealed two subgroups likely reflecting human subpopulations. Their sequences are tightly connected by homologous recombination. Our extensive analysis of RM systems revealed an extreme variability in DNA methyltransferases, especially in their target recognition domains. Their diversity was, however, not immediately related to the genome sequence diversity, except for very closely related strains. An interesting exception is a hybrid strain, which likely has conserved the methylation gene repertoire from one parent but diversified in sequence by massive acquisition of fragmentary DNA sequences from the other parent. Our results demonstrate how a bacterial population can be extremely divergent in epigenetics and yet homogenized in sequence.
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Affiliation(s)
- Kenji K Kojima
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, University of Tokyo, Minato-ku, Tokyo, Japan Institute of Medical Science, University of Tokyo, Tokyo, Japan Genetic Information Research Institute, Los Altos, CA Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, Tokyo, Japan
| | - Yoshikazu Furuta
- Institute of Medical Science, University of Tokyo, Tokyo, Japan Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, Tokyo, Japan
| | - Koji Yahara
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, University of Tokyo, Minato-ku, Tokyo, Japan Institute of Medical Science, University of Tokyo, Tokyo, Japan Department of Bacteriology II, National Institute of Infectious Diseases, Tokyo, Japan
| | - Masaki Fukuyo
- Institute of Medical Science, University of Tokyo, Tokyo, Japan Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, Tokyo, Japan
| | - Yuh Shiwa
- Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Tokyo, Japan
| | - Shin Nishiumi
- Division of Gastroenterology, Department of Internal Medicine, Graduate School of Medicine, Kobe University, Kobe, Japan
| | - Masaru Yoshida
- Division of Gastroenterology, Department of Internal Medicine, Graduate School of Medicine, Kobe University, Kobe, Japan
| | - Takeshi Azuma
- Division of Gastroenterology, Department of Internal Medicine, Graduate School of Medicine, Kobe University, Kobe, Japan
| | - Hirofumi Yoshikawa
- Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Tokyo, Japan Department of Bioscience, Tokyo University of Agriculture, Tokyo, Japan
| | - Ichizo Kobayashi
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, University of Tokyo, Minato-ku, Tokyo, Japan Institute of Medical Science, University of Tokyo, Tokyo, Japan Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, Tokyo, Japan
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20
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Zerbetto De Palma G, Mendiondo N, Wonaga A, Viola L, Ibarra D, Campitelli E, Salim N, Corti R, Goldman C, Catalano M. Occurrence of Mutations in the Antimicrobial Target Genes Related to Levofloxacin, Clarithromycin, and Amoxicillin Resistance in Helicobacter pylori Isolates from Buenos Aires City. Microb Drug Resist 2016; 23:351-358. [PMID: 27391421 DOI: 10.1089/mdr.2015.0361] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Domain V of 23S rRNA, gyrA and gyrB Quinolones Resistance-Determining Region (QRDR), and pbp-1A gene point mutations were investigated in Helicobacter pylori-resistant isolates from three centres of Buenos Aires. Minimal inhibitory concentrations (MICs) were performed in 197 isolates from 52 H. pylori-positive naive patients by agar dilution method. Point mutations were achieved by amplification and sequencing of the target genes, and their association with resistance was determined by natural transformation assays. Resistance rates were as follows: metronidazole 28.8%, clarithromycin (CLA) 26.9%, levofloxacin (LEV) 32.7%, and amoxicillin (AMX) 7.6%. Nearly one-third of patients carried multidrug-resistant isolates. A2143G or A2142G in domain V of 23S-rRNA was found in all isolates showing high level of resistance to CLA (MIC >2 mg/L), accounting for 76.0% (38/50) of those with the resistant phenotype. The mutations A2267G or T1861C carried by 8/12 isolates with MIC 1-2 mg/L (low level) did not confer resistance by transformation. Substitutions at GyrA position 87 or 91, mainly N87K and D91G, were found in 92.8% (52/56) of the LEV-resistant isolates: 48 isolates with MIC 4-64 mg/L and 4/8 isolates with MIC 2 mg/L. The remaining four harboured K133N, also present in susceptible isolates. None of the substitutions in GyrB demonstrated to confer resistance. Transformation proved that PBP-1A N562Y and/or T556S substitutions confer the AMX resistance in our isolates, showing an additive effect. In conclusion, the usually reported mutations related to CLA, LEV, and AMX resistance were found in our isolates. However, low-level CLA resistance seems not to be due to mutations in Domain V of 23S rRNA gene.
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Affiliation(s)
- Gerardo Zerbetto De Palma
- 1 Universidad de Buenos Aires, CONICET, Instituto de Microbiología y Parasitología Médica (IMPAM), Facultad de Medicina, Buenos Aires, Argentina
| | - Nicolas Mendiondo
- 1 Universidad de Buenos Aires, CONICET, Instituto de Microbiología y Parasitología Médica (IMPAM), Facultad de Medicina, Buenos Aires, Argentina
| | - Andrés Wonaga
- 2 Centro Integral de Gastroenterología , Buenos Aires, Argentina
| | - Luis Viola
- 2 Centro Integral de Gastroenterología , Buenos Aires, Argentina
| | - Daniela Ibarra
- 3 Servicio de Gastroenterología, Hospital Aeronáutico Central , Buenos Aires, Argentina
| | - Esteban Campitelli
- 3 Servicio de Gastroenterología, Hospital Aeronáutico Central , Buenos Aires, Argentina
| | - Nicolas Salim
- 4 Servicio de Estómago y Esófago, Hospital de Gastroenterología Bonorino Udaondo , Buenos Aires, Argentina
| | - Rodolfo Corti
- 4 Servicio de Estómago y Esófago, Hospital de Gastroenterología Bonorino Udaondo , Buenos Aires, Argentina
| | - Cinthia Goldman
- 5 Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Fisicomatematica, Cátedra de Física, Buenos Aires, Argentina
| | - Mariana Catalano
- 1 Universidad de Buenos Aires, CONICET, Instituto de Microbiología y Parasitología Médica (IMPAM), Facultad de Medicina, Buenos Aires, Argentina
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21
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Bubendorfer S, Krebes J, Yang I, Hage E, Schulz TF, Bahlawane C, Didelot X, Suerbaum S. Genome-wide analysis of chromosomal import patterns after natural transformation of Helicobacter pylori. Nat Commun 2016; 7:11995. [PMID: 27329939 PMCID: PMC4917963 DOI: 10.1038/ncomms11995] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 05/19/2016] [Indexed: 12/17/2022] Open
Abstract
Recombination plays a dominant role in the evolution of the bacterial pathogen Helicobacter pylori, but its dynamics remain incompletely understood. Here we use an in vitro transformation system combined with genome sequencing to study chromosomal integration patterns after natural transformation. A single transformation cycle results in up to 21 imports, and repeated transformations generate a maximum of 92 imports (8% sequence replacement). Import lengths show a bimodal distribution with averages of 28 and 1,645 bp. Reanalysis of paired H. pylori genomes from chronically infected people demonstrates the same bimodal import pattern in vivo. Restriction endonucleases (REases) of the recipient bacteria fail to inhibit integration of homeologous DNA, independently of methylation. In contrast, REases limit the import of heterologous DNA. We conclude that restriction-modification systems inhibit the genomic integration of novel sequences, while they pose no barrier to homeologous recombination, which reconciles the observed stability of the H. pylori gene content and its highly recombinational population structure. Uptake and integration of exogenous DNA into the bacterial genome play an important role in the evolution of the pathogen Helicobacter pylori. Here, the authors describe a bimodal pattern of chromosomal integration and show how restriction-modification systems limit the import of heterologous DNA.
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Affiliation(s)
- Sebastian Bubendorfer
- Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.,DZIF-German Center for Infection Research, Hannover-Braunschweig Site, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Juliane Krebes
- Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.,DZIF-German Center for Infection Research, Hannover-Braunschweig Site, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Ines Yang
- Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.,DZIF-German Center for Infection Research, Hannover-Braunschweig Site, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Elias Hage
- DZIF-German Center for Infection Research, Hannover-Braunschweig Site, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.,Institute of Virology, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Thomas F Schulz
- DZIF-German Center for Infection Research, Hannover-Braunschweig Site, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.,Institute of Virology, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Christelle Bahlawane
- Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Xavier Didelot
- Department of Infectious Disease Epidemiology, Imperial College, Norfolk Place, London W2 1PG, UK
| | - Sebastian Suerbaum
- Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.,DZIF-German Center for Infection Research, Hannover-Braunschweig Site, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
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22
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Cao Q, Didelot X, Wu Z, Li Z, He L, Li Y, Ni M, You Y, Lin X, Li Z, Gong Y, Zheng M, Zhang M, Liu J, Wang W, Bo X, Falush D, Wang S, Zhang J. Progressive genomic convergence of two Helicobacter pylori strains during mixed infection of a patient with chronic gastritis. Gut 2015; 64:554-61. [PMID: 25007814 PMCID: PMC4392222 DOI: 10.1136/gutjnl-2014-307345] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
OBJECTIVE To study the detailed nature of genomic microevolution during mixed infection with multiple Helicobacter pylori strains in an individual. DESIGN We sampled 18 isolates from a single biopsy from a patient with chronic gastritis and nephritis. Whole-genome sequencing was applied to these isolates, and statistical genetic tools were used to investigate their evolutionary history. RESULTS The genomes fall into two clades, reflecting colonisation of the stomach by two distinct strains, and these lineages have accumulated diversity during an estimated 2.8 and 4.2 years of evolution. We detected about 150 clear recombination events between the two clades. Recombination between the lineages is a continuous ongoing process and was detected on both clades, but the effect of recombination in one clade was nearly an order of magnitude higher than in the other. Imputed ancestral sequences also showed evidence of recombination between the two strains prior to their diversification, and we estimate that they have both been infecting the same host for at least 12 years. Recombination tracts between the lineages were, on average, 895 bp in length, and showed evidence for the interspersion of recipient sequences that has been observed in in vitro experiments. The complex evolutionary history of a phage-related protein provided evidence for frequent reinfection of both clades by a single phage lineage during the past 4 years. CONCLUSIONS Whole genome sequencing can be used to make detailed conclusions about the mechanisms of genetic change of H. pylori based on sampling bacteria from a single gastric biopsy.
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Affiliation(s)
- Qizhi Cao
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China,Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, China,Department of Immunology, Binzhou Medical University, Yantai, China
| | - Xavier Didelot
- Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| | - Zhongbiao Wu
- The First People's Hospital of Wenling, the Affiliated Wenling Hospital of Wenzhou Medical College, Zhejiang, China
| | - Zongwei Li
- Beijing Institute of Radiation Medicine, Beijing, China
| | - Lihua He
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China,Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, China
| | - Yunsheng Li
- The First People's Hospital of Wenling, the Affiliated Wenling Hospital of Wenzhou Medical College, Zhejiang, China
| | - Ming Ni
- Beijing Institute of Radiation Medicine, Beijing, China
| | - Yuanhai You
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China,Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, China
| | - Xi Lin
- The First People's Hospital of Wenling, the Affiliated Wenling Hospital of Wenzhou Medical College, Zhejiang, China
| | - Zhen Li
- Beijing Institute of Radiation Medicine, Beijing, China
| | - Yanan Gong
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China,Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, China
| | - Minqiao Zheng
- The First People's Hospital of Wenling, the Affiliated Wenling Hospital of Wenzhou Medical College, Zhejiang, China
| | - Minli Zhang
- Beijing Institute of Radiation Medicine, Beijing, China
| | - Jie Liu
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China,Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, China
| | - Weijun Wang
- The First People's Hospital of Wenling, the Affiliated Wenling Hospital of Wenzhou Medical College, Zhejiang, China
| | - Xiaochen Bo
- Beijing Institute of Radiation Medicine, Beijing, China
| | - Daniel Falush
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany,Graduate School of Frontier Sciences, University of Tokyo, Tokyo, Japan
| | - Shengqi Wang
- Beijing Institute of Radiation Medicine, Beijing, China
| | - Jianzhong Zhang
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China,Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, China
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23
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Mortimer TD, Pepperell CS. Genomic signatures of distributive conjugal transfer among mycobacteria. Genome Biol Evol 2014; 6:2489-500. [PMID: 25173757 PMCID: PMC4202316 DOI: 10.1093/gbe/evu175] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Distributive conjugal transfer (DCT) is a newly described mechanism of lateral gene transfer (LGT) that results in a mosaic transconjugant structure, similar to the products of meiosis. We have tested popular LGT detection methods on whole-genome sequence data from experimental DCT transconjugants and used the best performing methods to compare genomic signatures of DCT with those of LGT through natural transformation, conjugative plasmids, and mobile genetic elements (MGE). We found that DCT results in transfer of larger chromosomal segments, that these segments are distributed more broadly around the chromosome, and that a greater proportion of the chromosome is affected by DCT than by other mechanisms of LGT. We used the best performing methods to characterize LGT in Mycobacterium canettii, the mycobacterial species most closely related to Mycobacterium tuberculosis. Patterns of LGT among M. canettii were highly distinctive. Gene flow appeared unidirectional, from lineages with minimal evidence of LGT to isolates with a substantial proportion (6–13%) of sites identified as recombinant. Among M. canettii isolates with evidence of LGT, recombinant fragments were larger and more evenly distributed relative to bacteria that undergo LGT through natural transformation, conjugative plasmids, and MGE. Spatial bias in M. canettii was also unusual in that patterns of recombinant fragment sharing mirrored overall phylogenetic structure. Based on the proportion of recombinant sites, the size of recombinant fragments, their spatial distribution and lack of association with MGE, as well as unidirectionality of DNA transfer, we conclude that DCT is the predominant mechanism of LGT among M. canettii.
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Affiliation(s)
- Tatum D Mortimer
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison Microbiology Doctoral Training Program, University of Wisconsin-Madison
| | - Caitlin S Pepperell
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison Department of Medicine, Division of Infectious Diseases, University of Wisconsin-Madison
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24
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Krebes J, Didelot X, Kennemann L, Suerbaum S. Bidirectional genomic exchange between Helicobacter pylori strains from a family in Coventry, United Kingdom. Int J Med Microbiol 2014; 304:1135-46. [PMID: 25218701 DOI: 10.1016/j.ijmm.2014.08.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 08/06/2014] [Accepted: 08/10/2014] [Indexed: 02/08/2023] Open
Abstract
The human gastric pathogen Helicobacter pylori is characterised by a high mutation rate and frequent recombination during mixed infection, which result in extensive genetic diversity and rapid allelic diversification. Mixed infections are believed to be much more common in regions with a high H. pylori prevalence than in industrialised countries. To better understand the genomic flexibility of H. pylori in a low prevalence region, we used 454 sequencing technology to investigate whole genome sequences of H. pylori strains isolated from members of three generations of a family living in Coventry, UK. The genomes of four H. pylori strains isolated from a grandfather, two of his sons and one grandson were sequenced. Three of these genomes showed a high overall sequence similarity, suggesting a recent common ancestor. The genomes differed by 316-336 SNPs, and recombination events (imports) resulted in 170-251 clusters of polymorphisms (CNPs). Imports were particularly frequent in genes encoding Helicobacter outer membrane proteins, suggesting an adaptation of the strains to their individual host. The fourth strain differed substantially from these three highly related strains but still shared long fragments of identical sequence, which most likely reflect imports from the highly related family variants. The data show extensive bidirectional exchange of DNA between the strains isolated from the family members, illustrating both the convergence and divergence effect that recombination can lead to. Detailed analysis of the distribution of SNPs and imports permits to draw up a complex scenario of the transmission history involving infection with at least two, and probably more separate strains. This complexity and the resulting high frequency of recombination were unexpected for an industrialised country where the prevalence of H. pylori infection has strongly declined in recent decades.
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Affiliation(s)
- Juliane Krebes
- Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany; German Center for Infection Research, Hannover-Braunschweig Site, Carl-Neuberg-Straße 1, 30625 Hannover, Germany.
| | - Xavier Didelot
- Department of Infectious Disease Epidemiology, Imperial College London, London W2 1PG, United Kingdom.
| | - Lynn Kennemann
- Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany.
| | - Sebastian Suerbaum
- Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany; German Center for Infection Research, Hannover-Braunschweig Site, Carl-Neuberg-Straße 1, 30625 Hannover, Germany.
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25
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Donczew R, Mielke T, Jaworski P, Zakrzewska-Czerwińska J, Zawilak-Pawlik A. Assembly of Helicobacter pylori initiation complex is determined by sequence-specific and topology-sensitive DnaA-oriC interactions. J Mol Biol 2014; 426:2769-82. [PMID: 24862285 DOI: 10.1016/j.jmb.2014.05.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 05/15/2014] [Accepted: 05/16/2014] [Indexed: 10/25/2022]
Abstract
In bacteria, chromosome replication is initiated by binding of the DnaA initiator protein to DnaA boxes located in the origin of chromosomal replication (oriC). This leads to DNA helix opening within the DNA-unwinding element. Helicobacter pylori oriC, the first bipartite origin identified in Gram-negative bacteria, contains two subregions, oriC1 and oriC2, flanking the dnaA gene. The DNA-unwinding element region is localized in the oriC2 subregion downstream of dnaA. Surprisingly, oriC2-DnaA interactions were shown to depend on DNA topology, which is unusual in bacteria but is similar to initiator-origin interactions observed in higher organisms. In this work, we identified three DnaA boxes in the oriC2 subregion, two of which were bound only as supercoiled DNA. We found that all three DnaA boxes play important roles in orisome assembly and subsequent DNA unwinding, but different functions can be assigned to individual boxes. This suggests that the H. pylori oriC may be functionally divided, similar to what was described recently for Escherichia coli oriC. On the basis of these results, we propose a model of initiation complex formation in H. pylori.
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Affiliation(s)
- Rafał Donczew
- Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Department of Microbiology, Weigla 12, 53-114 Wrocław, Poland.
| | - Thorsten Mielke
- Max Planck Institute for Molecular Genetics, Ihnestrasse 63-73, 14195 Berlin, Germany.
| | - Paweł Jaworski
- Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Department of Microbiology, Weigla 12, 53-114 Wrocław, Poland.
| | - Jolanta Zakrzewska-Czerwińska
- Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Department of Microbiology, Weigla 12, 53-114 Wrocław, Poland; University of Wrocław, Faculty of Biotechnology, Joliot-Curie 14a, 50-138 Wrocław, Poland.
| | - Anna Zawilak-Pawlik
- Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Department of Microbiology, Weigla 12, 53-114 Wrocław, Poland.
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26
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Han D, Xu H, Puranik R, Xu Z. Natural transformation of Thermotoga sp. strain RQ7. BMC Biotechnol 2014; 14:39. [PMID: 24884561 PMCID: PMC4029938 DOI: 10.1186/1472-6750-14-39] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 05/02/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Thermotoga species are organisms of enormous interest from a biotechnological as well as evolutionary point of view. Genetic modifications of Thermotoga spp. are often desired in order to fully release their multifarious potentials. Effective transformation of recombinant DNA into these bacteria constitutes a critical step of such efforts. This study aims to establish natural competency in Thermotoga spp. and to provide a convenient method to transform these organisms. RESULTS Foreign DNA was found to be relatively stable in the supernatant of a Thermotoga culture for up to 6 hours. Adding donor DNA to T. sp. strain RQ7 at its early exponential growth phase (OD600 0.18 ~ 0.20) resulted in direct acquisition of the DNA by the cells. Both T. neapolitana chromosomal DNA and Thermotoga-E. coli shuttle vectors effectively transformed T. sp. strain RQ7, rendering the cells resistance to kanamycin. The kan gene carried by the shuttle vector pDH10 was detected by PCR from the plasmid extract of the transformants, and the amplicons were verified by restriction digestions. A procedure for natural transformation of Thermotoga spp. was established and optimized. With the optimized method, T. sp. strain RQ7 sustained a transformation frequency in the order of 10⁻⁷ with both genomic and plasmid DNA. CONCLUSIONS T. sp. strain RQ7 cells are naturally transformable during their early exponential phase. They acquire DNA from both closely and distantly related species. Both chromosomal DNA and plasmid DNA serve as suitable substrates for transformation. Our findings lend a convenient technical tool for the genetic engineering of Thermotoga spp.
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Affiliation(s)
| | | | | | - Zhaohui Xu
- Department of Biological Sciences, Bowling Green State University, 43403 Bowling Green, OH, USA.
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27
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Extensive cotransformation of natural variation into chromosomes of naturally competent Haemophilus influenzae. G3-GENES GENOMES GENETICS 2014; 4:717-31. [PMID: 24569039 PMCID: PMC4059242 DOI: 10.1534/g3.113.009597] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Naturally competent bacterial species actively take up environmental DNA and can incorporate it into their chromosomes by homologous recombination. This can bring genetic variation from environmental DNA to recipient chromosomes, often in multiple long “donor” segments. Here, we report the results of genome sequencing 96 colonies of a laboratory Haemophilus influenzae strain, which had been experimentally transformed by DNA from a diverged clinical isolate. Donor segments averaged 6.9 kb (spanning several genes) and were clustered into recombination tracts of ~19.5 kb. Individual colonies had replaced from 0.1 to 3.2% of their chromosomes, and ~1/3 of all donor-specific single-nucleotide variants were present in at least one recombinant. We found that nucleotide divergence did not obviously limit the locations of recombination tracts, although there were small but significant reductions in divergence at recombination breakpoints. Although indels occasionally transformed as parts of longer recombination tracts, they were common at breakpoints, suggesting that indels typically block progression of strand exchange. Some colonies had recombination tracts in which variant positions contained mixtures of both donor and recipient alleles. These tracts were clustered around the origin of replication and were interpreted as the result of heteroduplex segregation in the original transformed cell. Finally, a pilot experiment demonstrated the utility of natural transformation for genetically dissecting natural phenotypic variation. We discuss our results in the context of the potential to merge experimental and population genetic approaches, giving a more holistic understanding of bacterial gene transfer.
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28
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Abstract
Many bacteria are naturally competent, able to actively transport environmental DNA fragments across their cell envelope and into their cytoplasm. Because incoming DNA fragments can recombine with and replace homologous segments of the chromosome, competence provides cells with a potent mechanism of horizontal gene transfer as well as access to the nutrients in extracellular DNA. This review starts with an introductory overview of competence and continues with a detailed consideration of the DNA uptake specificity of competent proteobacteria in the Pasteurellaceae and Neisseriaceae. Species in these distantly related families exhibit strong preferences for genomic DNA from close relatives, a self-specificity arising from the combined effects of biases in the uptake machinery and genomic overrepresentation of the sequences this machinery prefers. Other competent species tested lack obvious uptake bias or uptake sequences, suggesting that strong convergent evolutionary forces have acted on these two families. Recent results show that uptake sequences have multiple "dialects," with clades within each family preferring distinct sequence variants and having corresponding variants enriched in their genomes. Although the genomic consensus uptake sequences are 12 and 29 to 34 bp, uptake assays have found that only central cores of 3 to 4 bp, conserved across dialects, are crucial for uptake. The other bases, which differ between dialects, make weaker individual contributions but have important cooperative interactions. Together, these results make predictions about the mechanism of DNA uptake across the outer membrane, supporting a model for the evolutionary accumulation and stability of uptake sequences and suggesting that uptake biases may be more widespread than currently thought.
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29
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Environmental determinants of transformation efficiency in Helicobacter pylori. J Bacteriol 2013; 196:337-44. [PMID: 24187089 DOI: 10.1128/jb.00633-13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Helicobacter pylori uses natural competence and homologous recombination to adapt to the dynamic environment of the stomach mucosa and maintain chronic colonization. Although H. pylori competence is constitutive, its rate of transformation is variable, and little is known about factors that influence it. To examine this, we first determined the transformation efficiency of H. pylori strains under low O2 (5% O2, 7.6% CO2, 7.6% H2) and high O2 (15% O2, 2.9% CO2, 2.9% H2) conditions using DNA containing an antibiotic resistance marker. H. pylori transformation efficiency was 6- to 32-fold greater under high O2 tension, which was robust across different H. pylori strains, genetic loci, and bacterial growth phases. Since changing the O2 concentration for these initial experiments also changed the concentrations of CO2 and H2, transformations were repeated under conditions where O2, CO2, and H2 were each varied individually. The results showed that the increase in transformation efficiency under high O2 was largely due to a decrease in CO2. An increase in pH similar to that caused by low CO2 was also sufficient to increase transformation efficiency. These results have implications for the physiology of H. pylori in the gastric environment, and they provide optimized conditions for the laboratory construction of H. pylori mutants using natural transformation.
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30
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Genomic evolution and transmission of Helicobacter pylori in two South African families. Proc Natl Acad Sci U S A 2013; 110:13880-5. [PMID: 23898187 DOI: 10.1073/pnas.1304681110] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Helicobacter pylori infects the stomachs of one in two humans and can cause sequelae that include ulcers and cancer. Here we sequenced the genomes of 97 H. pylori isolates from 52 members of two families living in rural conditions in South Africa. From each of 45 individuals, two H. pylori strains were isolated from the antrum and corpus parts of the stomach, and comparisons of their genomes enabled us to study within-host evolution. In 5 of these 45 hosts, the two genomes were too distantly related to be derived from each other and therefore represented evidence of multiple infections. From the remaining 40 genome pairs, we estimated that the synonymous mutation rate was 1.38 × 10(-5) per site per year, with a low effective population size within host probably reflecting population bottlenecks and immune selection. Some individuals showed very little evidence for recombination, whereas in others, recombination introduced up to 100-times more substitutions than mutation. These differences may reflect unequal opportunities for recombination depending on the presence or absence of multiple infections. Comparing the genomes carried by distinct individuals enabled us to establish probable transmission links. Transmission events were found significantly more frequently between close relatives, and between individuals living in the same house. We found, however, that a majority of individuals (27/52) were not linked by transmission to other individuals. Our results suggest that transmission does not always occur within families, and that coinfection with multiple strains is frequent and evolutionarily important despite a fast turnover of the infecting strains within-host.
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31
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Kung SH, Retchless AC, Kwan JY, Almeida RPP. Effects of DNA size on transformation and recombination efficiencies in Xylella fastidiosa. Appl Environ Microbiol 2013; 79:1712-7. [PMID: 23315739 PMCID: PMC3591940 DOI: 10.1128/aem.03525-12] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 01/02/2013] [Indexed: 11/20/2022] Open
Abstract
Horizontally transferred DNA acquired through transformation and recombination has the potential to contribute to the diversity and evolution of naturally competent bacteria. However, many different factors affect the efficiency with which DNA can be transformed and recombined. In this study, we determined how the size of both homologous and nonhomologous regions affects transformation and recombination efficiencies in Xylella fastidiosa, a naturally competent generalist pathogen responsible for many emerging plant diseases. Our experimental data indicate that 96 bp of flanking homology is sufficient to initiate recombination, with recombination efficiencies increasing exponentially with the size of the homologous flanking region up to 1 kb. Recombination efficiencies also decreased with the size of the nonhomologous insert, with no recombination detected when 6 kb of nonhomologous DNA was flanked on either side by 1 kb of homologous sequences. Upon analyzing sequenced X. fastidiosa subsp. fastidiosa genomes for evidence of allele conversion, we estimated the mean size of recombination events to be 1,906 bp, with each event modifying, on average, 1.79% of the nucleotides in the recombined region. There is increasing evidence that horizontally acquired genes significantly affect the genetic diversity of X. fastidiosa, and DNA acquired through natural transformation could be a prominent mode of this horizontal transfer.
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Affiliation(s)
| | - Adam C. Retchless
- Environmental Science, Policy, and Management, University of California, Berkeley, California, USA
| | - Jessica Y. Kwan
- Environmental Science, Policy, and Management, University of California, Berkeley, California, USA
| | - Rodrigo P. P. Almeida
- Environmental Science, Policy, and Management, University of California, Berkeley, California, USA
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32
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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: 383] [Impact Index Per Article: 34.8] [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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33
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Dwivedi GR, Sharma E, Rao DN. Helicobacter pylori DprA alleviates restriction barrier for incoming DNA. Nucleic Acids Res 2013; 41:3274-88. [PMID: 23355610 PMCID: PMC3597690 DOI: 10.1093/nar/gkt024] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Helicobacter pylori is a Gram-negative bacterium that colonizes human stomach and causes gastric inflammation. The species is naturally competent and displays remarkable diversity. The presence of a large number of restriction-modification (R-M) systems in this bacterium creates a barrier against natural transformation by foreign DNA. Yet, mechanisms that protect incoming double-stranded DNA (dsDNA) from restriction enzymes are not well understood. A DNA-binding protein, DNA Processing Protein A (DprA) has been shown to facilitate natural transformation of several Gram-positive and Gram-negative bacteria by protecting incoming single-stranded DNA (ssDNA) and promoting RecA loading on it. However, in this study, we report that H. pylori DprA (HpDprA) binds not only ssDNA but also dsDNA thereby conferring protection to both from various exonucleases and Type II restriction enzymes. Here, we observed a stimulatory role of HpDprA in DNA methylation through physical interaction with methyltransferases. Thus, HpDprA displayed dual functional interaction with H. pylori R-M systems by not only inhibiting the restriction enzymes but also stimulating methyltransferases. These results indicate that HpDprA could be one of the factors that modulate the R-M barrier during inter-strain natural transformation in H. pylori.
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34
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Kong Y, Ma JH, Warren K, Tsang RS, Low DE, Jamieson FB, Alexander DC, Hao W. Homologous recombination drives both sequence diversity and gene content variation in Neisseria meningitidis. Genome Biol Evol 2013; 5:1611-27. [PMID: 23902748 PMCID: PMC3787668 DOI: 10.1093/gbe/evt116] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/23/2013] [Indexed: 01/13/2023] Open
Abstract
The study of genetic and phenotypic variation is fundamental for understanding the dynamics of bacterial genome evolution and untangling the evolution and epidemiology of bacterial pathogens. Neisseria meningitidis (Nm) is among the most intriguing bacterial pathogens in genomic studies due to its dynamic population structure and complex forms of pathogenicity. Extensive genomic variation within identical clonal complexes (CCs) in Nm has been recently reported and suggested to be the result of homologous recombination, but the extent to which recombination contributes to genomic variation within identical CCs has remained unclear. In this study, we sequenced two Nm strains of identical serogroup (C) and multi-locus sequence type (ST60), and conducted a systematic analysis with an additional 34 Nm genomes. Our results revealed that all gene content variation between the two ST60 genomes was introduced by homologous recombination at the conserved flanking genes, and 94.25% or more of sequence divergence was caused by homologous recombination. Recombination was found in genes associated with virulence factors, antigenic outer membrane proteins, and vaccine targets, suggesting an important role of homologous recombination in rapidly altering the pathogenicity and antigenicity of Nm. Recombination was also evident in genes of the restriction and modification systems, which may undermine barriers to DNA exchange. In conclusion, homologous recombination can drive both gene content variation and sequence divergence in Nm. These findings shed new light on the understanding of the rapid pathoadaptive evolution of Nm and other recombinogenic bacterial pathogens.
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Affiliation(s)
- Ying Kong
- Department of Biological Sciences, Wayne State University
| | - Jennifer H. Ma
- Public Health Laboratories, Public Health Ontario, Toronto, Ontario, Canada
| | - Keisha Warren
- Public Health Laboratories, Public Health Ontario, Toronto, Ontario, Canada
- Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Raymond S.W. Tsang
- National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada
| | - Donald E. Low
- Public Health Laboratories, Public Health Ontario, Toronto, Ontario, Canada
- Mount Sinai Hospital, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Frances B. Jamieson
- Public Health Laboratories, Public Health Ontario, Toronto, Ontario, Canada
- Mount Sinai Hospital, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - David C. Alexander
- Public Health Laboratories, Public Health Ontario, Toronto, Ontario, Canada
- Mount Sinai Hospital, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Weilong Hao
- Department of Biological Sciences, Wayne State University
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35
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Antimicrobial susceptibility and resistance patterns among Helicobacter pylori strains from The Gambia, West Africa. Antimicrob Agents Chemother 2012; 57:1231-7. [PMID: 23263004 DOI: 10.1128/aac.00517-12] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Helicobacter pylori is a globally important and genetically diverse gastric pathogen that infects most people in developing countries. Eradication efforts are complicated by antibiotic resistance, which varies in frequency geographically. There are very few data on resistance in African strains. Sixty-four Gambian H. pylori strains were tested for antibiotic susceptibility. The role of rdxA in metronidazole (Mtz) susceptibility was tested by DNA transformation and sequencing; RdxA protein variants were interpreted in terms of RdxA structure. Forty-four strains (69%) were resistant to at least 8 μg of Mtz/ml. All six strains from infants, but only 24% of strains from adults, were sensitive (P = 0.0031). Representative Mtz-resistant (Mtz(r)) strains were rendered Mtz susceptible (Mtz(s)) by transformation with a functional rdxA gene; conversely, Mtz(s) strains were rendered Mtz(r) by rdxA inactivation. Many mutations were found by Gambian H. pylori rdxA sequencing; mutations that probably inactivated rdxA in Mtz(r) strains were identified and explained using RdxA protein's structure. All of the strains were sensitive to clarithromycin and erythromycin. Amoxicillin and tetracycline resistance was rare. Sequence analysis indicated that most tetracycline resistance, when found, was not due to 16S rRNA gene mutations. These data suggest caution in the use of Mtz-based therapies in The Gambia. The increasing use of macrolides against respiratory infections in The Gambia calls for continued antibiotic susceptibility monitoring. The rich variety of rdxA mutations that we found will be useful in further structure-function studies of RdxA, the enzyme responsible for Mtz susceptibility in this important pathogen.
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36
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Multiple pathways of plasmid DNA transfer in Helicobacter pylori. PLoS One 2012; 7:e45623. [PMID: 23029142 PMCID: PMC3447787 DOI: 10.1371/journal.pone.0045623] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2012] [Accepted: 08/20/2012] [Indexed: 01/25/2023] Open
Abstract
Many Helicobacter pylori (Hp) strains carry cryptic plasmids of different size and gene content, the function of which is not well understood. A subgroup of these plasmids (e.g. pHel4, pHel12), contain a mobilisation region, but no cognate type IV secretion system (T4SS) for conjugative transfer. Instead, certain H. pylori strains (e.g. strain P12 carrying plasmid pHel12) can harbour up to four T4SSs in their genome (cag-T4SS, comB, tfs3, tfs4). Here, we show that such indigenous plasmids can be efficiently transferred between H. pylori strains, even in the presence of extracellular DNaseI eliminating natural transformation. Knockout of a plasmid-encoded mobA relaxase gene significantly reduced plasmid DNA transfer in the presence of DNaseI, suggesting a DNA conjugation or mobilisation process. To identify the T4SS involved in this conjugative DNA transfer, each individual T4SS was consecutively deleted from the bacterial chromosome. Using a marker-free counterselectable gene deletion procedure (rpsL counterselection method), a P12 mutant strain was finally obtained with no single T4SS (P12ΔT4SS). Mating experiments using these mutants identified the comB T4SS in the recipient strain as the major mediator of plasmid DNA transfer between H. pylori strains, both in a DNaseI-sensitive (natural transformation) as well as a DNaseI-resistant manner (conjugative transfer). However, transfer of a pHel12::cat plasmid from a P12ΔT4SS donor strain into a P12ΔT4SS recipient strain provided evidence for the existence of a third, T4SS-independent mechanism of DNA transfer. This novel type of plasmid DNA transfer, designated as alternate DNaseI-Resistant (ADR) mechanism, is observed at a rather low frequency under in vitro conditions. Taken together, our study describes for the first time the existence of three distinct pathways of plasmid DNA transfer between H. pylori underscoring the importance of horizontal gene transfer for this species.
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Mao D, Grogan DW. Heteroduplex formation, mismatch resolution, and genetic sectoring during homologous recombination in the hyperthermophilic archaeon sulfolobus acidocaldarius. Front Microbiol 2012; 3:192. [PMID: 22679441 PMCID: PMC3367456 DOI: 10.3389/fmicb.2012.00192] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 05/11/2012] [Indexed: 11/25/2022] Open
Abstract
Hyperthermophilic archaea exhibit certain molecular-genetic features not seen in bacteria or eukaryotes, and their systems of homologous recombination (HR) remain largely unexplored in vivo. We transformed a Sulfolobus acidocaldariuspyrE mutant with short DNAs that contained multiple non-selected genetic markers within the pyrE gene. From 20 to 40% of the resulting colonies were found to contain two Pyr+ clones with distinct sets of the non-selected markers. The dual-genotype colonies could not be attributed to multiple DNAs entering the cells, or to conjugation between transformed and non-transformed cells. These colonies thus appear to represent genetic sectoring in which regions of heteroduplex DNA formed and then segregated after partial resolution of inter-strand differences. Surprisingly, sectoring was also frequent in cells transformed with single-stranded DNAs. Oligonucleotides produced more sectored transformants when electroporated as single strands than as a duplex, although all forms of donor DNA (positive-strand, negative-strand, and duplex) produced a diversity of genotypes, despite the limited number of markers. The marker patterns in the recombinants indicate that S. acidocaldarius resolves individual mismatches through un-coordinated short-patch excision followed by re-filling of the resulting gap. The conversion events that occur during transformation by single-stranded DNA do not show the strand bias necessary for a system that corrects replication errors effectively; similar events also occur in pre-formed heteroduplex electroporated into the cells. Although numerous mechanistic details remain obscure, the results demonstrate that the HR system of S. acidocaldarius can generate remarkable genetic diversity from short intervals of moderately diverged DNAs.
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Affiliation(s)
- Dominic Mao
- Department of Biological Sciences, University of Cincinnati Cincinnati, OH, USA
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DprB facilitates inter- and intragenomic recombination in Helicobacter pylori. J Bacteriol 2012; 194:3891-903. [PMID: 22609923 DOI: 10.1128/jb.00346-12] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
For naturally competent microorganisms, such as Helicobacter pylori, the steps that permit recombination of exogenous DNA are not fully understood. Immediately downstream of an H. pylori gene (dprA) that facilitates high-frequency natural transformation is HP0334 (dprB), annotated to be a putative Holliday junction resolvase (HJR). We showed that the HP0334 (dprB) gene product facilitates high-frequency natural transformation. We determined the physiologic roles of DprB by genetic analyses. DprB controls in vitro growth, survival after exposure to UV or fluoroquinolones, and intragenomic recombination. dprB ruvC double deletion dramatically decreases both homologous and homeologous transformation and survival after exposure to DNA-damaging agents. Moreover, the DprB protein binds to synthetic Holliday junction structures rather than double-stranded or single-stranded DNA. These results demonstrate that the dprB product plays important roles affecting inter- and intragenomic recombination. We provide evidence that the two putative H. pylori HJRs (DprB and RuvC) have overlapping but distinct functions involving intergenomic (primarily DprB) and intragenomic (primarily RuvC) recombination.
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Moccia C, Krebes J, Kulick S, Didelot X, Kraft C, Bahlawane C, Suerbaum S. The nucleotide excision repair (NER) system of Helicobacter pylori: role in mutation prevention and chromosomal import patterns after natural transformation. BMC Microbiol 2012; 12:67. [PMID: 22559785 PMCID: PMC3438104 DOI: 10.1186/1471-2180-12-67] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Accepted: 04/24/2012] [Indexed: 01/22/2023] Open
Abstract
Background Extensive genetic diversity and rapid allelic diversification are characteristics of the human gastric pathogen Helicobacter pylori, and are believed to contribute to its ability to cause chronic infections. Both a high mutation rate and frequent imports of short fragments of exogenous DNA during mixed infections play important roles in generating this allelic diversity. In this study, we used a genetic approach to investigate the roles of nucleotide excision repair (NER) pathway components in H. pylori mutation and recombination. Results Inactivation of any of the four uvr genes strongly increased the susceptibility of H. pylori to DNA damage by ultraviolet light. Inactivation of uvrA and uvrB significantly decreased mutation frequencies whereas only the uvrA deficient mutant exhibited a significant decrease of the recombination frequency after natural transformation. A uvrC mutant did not show significant changes in mutation or recombination rates; however, inactivation of uvrC promoted the incorporation of significantly longer fragments of donor DNA (2.2-fold increase) into the recipient chromosome. A deletion of uvrD induced a hyper-recombinational phenotype. Conclusions Our data suggest that the NER system has multiple functions in the genetic diversification of H. pylori, by contributing to its high mutation rate, and by controlling the incorporation of imported DNA fragments after natural transformation.
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Affiliation(s)
- Claudia Moccia
- Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Hannover, Germany
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Natural transformation of an engineered Helicobacter pylori strain deficient in type II restriction endonucleases. J Bacteriol 2012; 194:3407-16. [PMID: 22522893 DOI: 10.1128/jb.00113-12] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Restriction-modification (RM) systems are important for bacteria to limit foreign DNA invasion. The naturally competent bacterium Helicobacter pylori has highly diverse strain-specific type II systems. To evaluate the roles of strain-specific restriction in H. pylori natural transformation, a markerless type II restriction endonuclease-deficient (REd) mutant was constructed. We deleted the genes encoding all four active type II restriction endonucleases in H. pylori strain 26695 using sacB-mediated counterselection. Transformation by donor DNA with exogenous cassettes methylated by Escherichia coli was substantially (1.7 and 2.0 log(10) for cat and aphA, respectively) increased in the REd strain. There also was significantly increased transformation of the REd strain by donor DNA from other H. pylori strains, to an extent corresponding to their shared type II R-M system strain specificity with 26695. Comparison of the REd and wild-type strains indicates that restriction did not affect the length of DNA fragment integration during natural transformation. There also were no differentials in cell growth or susceptibility to DNA damage. In total, the data indicate that the type II REd mutant has enhanced competence with no loss of growth or repair facility compared to the wild type, facilitating H. pylori mutant construction and other genetic engineering.
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Abstract
All organisms have pathways that repair the genome, ensuring their survival and that of their progeny. But these pathways also serve to diversify the genome, causing changes at the nucleotide, whole gene, and genome structure levels. Sequencing of bacteria has revealed wide allelic diversity and differences in gene content within the same species, highlighting the importance of understanding pathways of recombination and DNA repair. The human stomach pathogen Helicobacter pylori is an excellent model system for studying these pathways. H. pylori harbors major recombination and repair pathways and is naturally competent, facilitating its ability to diversify its genome. Elucidation of DNA recombination, repair, and diversification programs in this pathogen will reveal connections between these pathways and their importance to infection.
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Affiliation(s)
- Marion S Dorer
- Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109-1024, USA.
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Dominguez-Bello MG, Blaser MJ. The Human Microbiota as a Marker for Migrations of Individuals and Populations. ANNUAL REVIEW OF ANTHROPOLOGY 2011. [DOI: 10.1146/annurev-anthro-081309-145711] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - Martin J. Blaser
- Departments of Medicine and Microbiology, New York University Langone Medical Center, New York, NY 10016;
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Pervasive recombination and sympatric genome diversification driven by frequency-dependent selection in Borrelia burgdorferi, the Lyme disease bacterium. Genetics 2011; 189:951-66. [PMID: 21890743 DOI: 10.1534/genetics.111.130773] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
How genomic diversity within bacterial populations originates and is maintained in the presence of frequent recombination is a central problem in understanding bacterial evolution. Natural populations of Borrelia burgdorferi, the bacterial agent of Lyme disease, consist of diverse genomic groups co-infecting single individual vertebrate hosts and tick vectors. To understand mechanisms of sympatric genome differentiation in B. burgdorferi, we sequenced and compared 23 genomes representing major genomic groups in North America and Europe. Linkage analysis of >13,500 single-nucleotide polymorphisms revealed pervasive horizontal DNA exchanges. Although three times more frequent than point mutation, recombination is localized and weakly affects genome-wide linkage disequilibrium. We show by computer simulations that, while enhancing population fitness, recombination constrains neutral and adaptive divergence among sympatric genomes through periodic selective sweeps. In contrast, simulations of frequency-dependent selection with recombination produced the observed pattern of a large number of sympatric genomic groups associated with major sequence variations at the selected locus. We conclude that negative frequency-dependent selection targeting a small number of surface-antigen loci (ospC in particular) sufficiently explains the maintenance of sympatric genome diversity in B. burgdorferi without adaptive divergence. We suggest that pervasive recombination makes it less likely for local B. burgdorferi genomic groups to achieve host specialization. B. burgdorferi genomic groups in the northeastern United States are thus best viewed as constituting a single bacterial species, whose generalist nature is a key to its rapid spread and human virulence.
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Mell JC, Shumilina S, Hall IM, Redfield RJ. Transformation of natural genetic variation into Haemophilus influenzae genomes. PLoS Pathog 2011; 7:e1002151. [PMID: 21829353 PMCID: PMC3145789 DOI: 10.1371/journal.ppat.1002151] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2011] [Accepted: 05/20/2011] [Indexed: 11/18/2022] Open
Abstract
Many bacteria are able to efficiently bind and take up double-stranded DNA fragments, and the resulting natural transformation shapes bacterial genomes, transmits antibiotic resistance, and allows escape from immune surveillance. The genomes of many competent pathogens show evidence of extensive historical recombination between lineages, but the actual recombination events have not been well characterized. We used DNA from a clinical isolate of Haemophilus influenzae to transform competent cells of a laboratory strain. To identify which of the ∼40,000 polymorphic differences had recombined into the genomes of four transformed clones, their genomes and their donor and recipient parents were deep sequenced to high coverage. Each clone was found to contain ∼1000 donor polymorphisms in 3–6 contiguous runs (8.1±4.5 kb in length) that collectively comprised ∼1–3% of each transformed chromosome. Seven donor-specific insertions and deletions were also acquired as parts of larger donor segments, but the presence of other structural variation flanking 12 of 32 recombination breakpoints suggested that these often disrupt the progress of recombination events. This is the first genome-wide analysis of chromosomes directly transformed with DNA from a divergent genotype, connecting experimental studies of transformation with the high levels of natural genetic variation found in isolates of the same species. The ability of bacteria to acquire genetic information from their relatives—called natural competence—poses a major health risk, since recombination between pathogenic bacterial lineages can help bacteria develop resistance to antibiotics and adapt to host defenses. In this study we transformed competent cells of the human pathogen Haemophilus influenzae with genomic DNA from a divergent clinical isolate and used deep sequencing to identify the recombination events in four transformed chromosomes. The results show that transformation of single competent cells is more extensive than expected, and suggests that transformation can be used as a tool to map traits that vary between clinical isolates.
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Affiliation(s)
- Joshua Chang Mell
- University of British Columbia, Department of Zoology, Vancouver, British Columbia, Canada
| | - Svetlana Shumilina
- University of Virginia School of Medicine, Department of Biochemistry and Molecular Genetics, Charlottesville, Virginia, United States of America
| | - Ira M. Hall
- University of Virginia School of Medicine, Department of Biochemistry and Molecular Genetics, Charlottesville, Virginia, United States of America
| | - Rosemary J. Redfield
- University of British Columbia, Department of Zoology, Vancouver, British Columbia, Canada
- * E-mail:
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Abstract
High genetic diversity is a hallmark of the gastric pathogen Helicobacter pylori. We used 454 sequencing technology to perform whole-genome comparisons for five sets of H. pylori strains that had been sequentially cultured from four chronically infected Colombians (isolation intervals=3-16 y) and one human volunteer experimentally infected with H. pylori as part of a vaccine trial. The four sets of genomes from Colombian H. pylori differed by 27-232 isolated SNPs and 16-441 imported clusters of polymorphisms resulting from recombination. Imports (mean length=394 bp) were distributed nonrandomly over the chromosome and frequently occurred in groups, suggesting that H. pylori first takes up long DNA fragments, which subsequently become partially integrated in multiple shorter pieces. Imports were present at significantly increased frequency in members of the hop family of outer membrane gene paralogues, some of which are involved in bacterial adhesion, suggesting diversifying selection. No evidence of recombination and few other differences were identified in the strain pair from an infected volunteer, indicating that the H. pylori genome is stable in the absence of mixed infection. Among these few differences was an OFF/ON switch in the phase-variable adhesin gene hopZ, suggesting strong in vivo selection for this putative adhesin during early colonization.
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Neisseria meningitidis is structured in clades associated with restriction modification systems that modulate homologous recombination. Proc Natl Acad Sci U S A 2011; 108:4494-9. [PMID: 21368196 DOI: 10.1073/pnas.1019751108] [Citation(s) in RCA: 153] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Molecular data on a limited number of chromosomal loci have shown that the population of Neisseria meningitidis (Nm), a deadly human pathogen, is structured in distinct lineages. Given that the Nm population undergoes substantial recombination, the mechanisms resulting in the evolution of these lineages, their persistence in time, and the implications for the pathogenicity of the bacterium are not yet completely understood. Based on whole-genome sequencing, we show that Nm is structured in phylogenetic clades. Through acquisition of specific genes and through insertions and rearrangements, each clade has acquired and remodeled specific genomic tracts, with the potential to impact on the commensal and virulence behavior of Nm. Despite this clear evidence of a structured population, we confirm high rates of detectable recombination throughout the whole Nm chromosome. However, gene conversion events were found to be longer within clades than between clades, suggesting a DNA cleavage mechanism associated with the phylogeny of the species. We identify 22 restriction modification systems, probably acquired by horizontal gene transfer from outside of the species/genus, whose distribution in the different strains coincides with the phylogenetic clade structure. We provide evidence that these clade-associated restriction modification systems generate a differential barrier to DNA exchange consistent with the observed population structure. These findings have general implications for the emergence of lineage structure and virulence in recombining bacterial populations, and they could provide an evolutionary framework for the population biology of a number of other bacterial species that show contradictory population structure and dynamics.
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Wang G, Lo LF, Maier RJ. The RecRO pathway of DNA recombinational repair in Helicobacter pylori and its role in bacterial survival in the host. DNA Repair (Amst) 2011; 10:373-9. [PMID: 21292567 DOI: 10.1016/j.dnarep.2011.01.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2010] [Revised: 12/23/2010] [Accepted: 01/04/2011] [Indexed: 12/20/2022]
Abstract
Two pathways for DNA recombination, AddAB (RecBCD-like) and RecRO, were identified in Helicobacter pylori, a pathogenic bacterium that colonizes human stomachs resulting in a series of gastric diseases. In this study, we examined the physiological roles of H. pylori RecRO pathway in DNA recombinational repair. We characterized H. pylori single mutants in recR and in recO, genes in the putative gap repair recombination pathway, and an addA recO double mutant that is thus deficient in both pathways that initiate DNA recombinational repair. The recR or recO single mutants showed the same level of sensitivity to mitomycin C as the parent strain, suggesting that the RecRO pathway is not responsible for the repair of DNA double strand breaks. However, H. pylori recR and recO mutants are highly sensitive to oxidative stress and separately to acid stress, two major stress conditions that H. pylori encounters in its physiological niche. The complementation of the recR mutant restored the sensitivity to oxidative and acid stress to the wild type level. By measuring DNA transformation frequencies, the recR and recO single mutants were shown to have no effect on inter-genomic recombination, whereas the addA recO double mutant had a greatly (∼12-fold) reduced transformation frequency. On the other hand, the RecRO pathway was shown to play a significant role in intra-genomic recombination with direct repeat sequences. Whereas the recA strain had a deletion frequency 35-fold lower than that of background level, inactivation of recR resulted in a 4-fold decrease in deletion frequency. In a mouse infection model, the three mutant strains displayed a greatly reduced ability to colonize the host stomachs. The geometric means of colonization number for the wild type, recR, recO, and addA recO strains were 6 x 10⁵, 1.6 x 10⁴, 1.4 x 10⁴ and 4 x 10³ CFU/g stomach, respectively. H. pylori RecRO-mediated DNA recombinational repair (intra-genomic recombination) is thus involved in repairing DNA damage induced by oxidative and acid stresses and plays an important role in bacterial survival and persistent colonization in the host.
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Affiliation(s)
- Ge Wang
- Department of Microbiology, 815 Biological Sciences Building, University of Georgia, Athens, GA 30602, USA
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Humbert O, Dorer MS, Salama NR. Characterization of Helicobacter pylori factors that control transformation frequency and integration length during inter-strain DNA recombination. Mol Microbiol 2010; 79:387-401. [PMID: 21219459 DOI: 10.1111/j.1365-2958.2010.07456.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Helicobacter pylori is a genetically diverse bacterial species, owing in part to its natural competence for DNA uptake that facilitates recombination between strains. Inter-strain DNA recombination occurs during human infection and the H. pylori genome is in linkage equilibrium worldwide. Despite this high propensity for DNA exchange, little is known about the factors that limit the extent of recombination during natural transformation. Here, we identify restriction-modification (R-M) systems as a barrier to transformation with homeologous DNA and find that R-M systems and several components of the recombination machinery control integration length. Type II R-M systems, the nuclease nucT and resolvase ruvC reduced integration length whereas the helicase recG increased it. In addition, we characterized a new factor that promotes natural transformation in H. pylori, dprB. Although free recombination has been widely observed in H. pylori, our study suggests that this bacterium uses multiple systems to limit inter-strain recombination.
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Affiliation(s)
- Olivier Humbert
- Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
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Microevolution of Helicobacter pylori during prolonged infection of single hosts and within families. PLoS Genet 2010; 6:e1001036. [PMID: 20661309 PMCID: PMC2908706 DOI: 10.1371/journal.pgen.1001036] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Accepted: 06/21/2010] [Indexed: 12/30/2022] Open
Abstract
Our understanding of basic evolutionary processes in bacteria is still very limited. For example, multiple recent dating estimates are based on a universal inter-species molecular clock rate, but that rate was calibrated using estimates of geological dates that are no longer accepted. We therefore estimated the short-term rates of mutation and recombination in Helicobacter pylori by sequencing an average of 39,300 bp in 78 gene fragments from 97 isolates. These isolates included 34 pairs of sequential samples, which were sampled at intervals of 0.25 to 10.2 years. They also included single isolates from 29 individuals (average age: 45 years) from 10 families. The accumulation of sequence diversity increased with time of separation in a clock-like manner in the sequential isolates. We used Approximate Bayesian Computation to estimate the rates of mutation, recombination, mean length of recombination tracts, and average diversity in those tracts. The estimates indicate that the short-term mutation rate is 1.4×10−6 (serial isolates) to 4.5×10−6 (family isolates) per nucleotide per year and that three times as many substitutions are introduced by recombination as by mutation. The long-term mutation rate over millennia is 5–17-fold lower, partly due to the removal of non-synonymous mutations due to purifying selection. Comparisons with the recent literature show that short-term mutation rates vary dramatically in different bacterial species and can span a range of several orders of magnitude. Mutation rates in bacteria have generally been considered to be much slower than in viruses. This is partly because estimates of long-term mutation rates for the evolution of distinct species have been inappropriately used for dating divergence within species. Furthermore, the most commonly used long-term mutation rate is based on geological dates that are no longer accepted. In addition, only few short-term mutation rates have been calculated within bacterial species, and these differ with the species by several orders of magnitude. Here, we provide robust estimates for short-term mutation and recombination rates within Helicobacter pylori, a bacterium that commonly infects the human gastric mucosa, based on serial isolates from long-term infections and on differences between isolates from multiple family members. These short-term mutation rates are 5–17-fold faster than long-term mutation rates in H. pylori that have been calibrated by parallel ancient migrations of humans. Short-term mutation rates in bacteria, including those for H. pylori, can be quite fast, partially overlapping with those for viruses. Future calculations of ages of bacterial species will need to account for dramatic differences in mutation rate between species and for dramatic differences between short- and long-term mutation rates.
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Discontinuity and limited linkage in the homologous recombination system of a hyperthermophilic archaeon. J Bacteriol 2010; 192:4660-8. [PMID: 20644140 DOI: 10.1128/jb.00447-10] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Genetic transformation of Sulfolobus acidocaldarius by a multiply marked pyrE gene provided a high-resolution assay of homologous recombination in a hyperthermophilic archaeon. Analysis of 100 Pyr(+) transformants revealed that this recombination system could transfer each of 23 nonselected base pair substitutions to the recipient chromosome along with the selected marker. In 30% of the recombinants, donor markers were transferred as multiple blocks. In at least 40% of the recombinants, donor markers separated by 5 or 6 bp segregated from each other, whereas similar markers separated by 2 bp did not segregate. Among intermarker intervals, the frequency of recombination tract endpoints varied 40-fold, but in contrast to other recombination systems, it did not correlate with the length of the interval. The average length of donor tracts (161 bp) and the frequent generation of multiple tracts seemed generally consistent with the genetic properties observed previously in S. acidocaldarius conjugation. The efficiency with which short intervals of diverged pyrE sequence were incorporated into the genome raises questions about the threat of ectopic recombination in Sulfolobus spp. mediated by this apparently efficient yet permissive system.
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