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Wiesner RS, Hendrixson DR, DiRita VJ. Natural transformation of Campylobacter jejuni requires components of a type II secretion system. J Bacteriol 2003; 185:5408-18. [PMID: 12949093 PMCID: PMC193740 DOI: 10.1128/jb.185.18.5408-5418.2003] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The human pathogen Campylobacter jejuni is one of more than 40 naturally competent bacterial species able to import macromolecular DNA from the environment and incorporate it into their genomes. However, in C. jejuni little is known about the genes involved in this process. We used random transposon mutagenesis to identify genes that are required for the transformation of this organism. We isolated mutants with insertions in 11 different genes; most of the mutants are affected in the DNA uptake stage of transformation, whereas two mutants are affected in steps subsequent to DNA uptake, such as recombination into the chromosome or in DNA transport across the inner membrane. Several of these genes encode proteins homologous to those involved in type II secretion systems, biogenesis of type IV pili, and competence for natural transformation in gram-positive and gram-negative species. Other genes identified in our screen encode proteins unique to C. jejuni or are homologous to proteins that have not been shown to play a role in the transformation in other bacteria.
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Affiliation(s)
- Rebecca S Wiesner
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0620, USA
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52
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Hofreuter D, Karnholz A, Haas R. Topology and membrane interaction of Helicobacter pylori ComB proteins involved in natural transformation competence. Int J Med Microbiol 2003; 293:153-65. [PMID: 12868652 DOI: 10.1078/1438-4221-00258] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The human gastric pathogen Helicobacter pylori is naturally competent for genetic transformation. The H. pylori comB gene duster encodes the VirB4-homologous ATPase ComB4 and the structural proteins ComB7-ComB10, which share significant sequence identity to the Agrobacterium tumefaciens virB-encoded type IV secretion system. To study the topology of the ComB7-10 proteins, we applied TnMax transposon mutagenesis by generating fusions of ComB proteins with mature beta-lactamase (BlaM) or alkaline phosphatase (PhoA). Our data show that the putative lipoprotein ComB7 is secreted and is found membrane-attached, probably by its lipid anchor. According to our topology mapping ComB8 is a bitopic membrane protein with a short N-terminal portion in the cytoplasm and the remainder of the protein expanding into the periplasmic space. ComB9 was verified as a periplasmic protein, tightly attached to the membrane. The N-terminus of ComB10 is anchored in the cytoplasmic membrane and the major portion of the protein, including a putative coiled-coil domain, is located in the periplasm. Limited protease digestion and protein extraction under different salt and pH conditions confirmed the periplasmic localization and the tight membrane association of the ComB protein complex. A hypothetical model of the ComB DNA transformation pore in H. pylori is presented.
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Affiliation(s)
- Dirk Hofreuter
- Max von Pettenkofer Institut für Hygiene und Medizinische Mikrobiologie, LMU München, München, Germany.
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53
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McGowan CC, Necheva AS, Forsyth MH, Cover TL, Blaser MJ. Promoter analysis of Helicobacter pylori genes with enhanced expression at low pH. Mol Microbiol 2003; 48:1225-39. [PMID: 12787351 DOI: 10.1046/j.1365-2958.2003.03500.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
To identify Helicobacter pylori genes with expression that is enhanced under low pH conditions, we used subtractive hybridization methodology. We identified 28 acid-induced genes, of which 18 have known or putative functions. Six pairs of genes were co-transcribed. Primer extension analysis identified single or multiple transcriptional start points (tsp) for 14 of the 22 loci. Sequence analysis of the -10 regions upstream of the tsps revealed consensus motifs for multiple RNA polymerase sigma factors present in H. pylori (sigma80, sigma54 and sigma28). No sequences resembling the -35 Escherichia coli consensus sequence (TTGACA) were present upstream of any of the genes. Both increased gene transcription and decreased mRNA decay contribute to the observed increase in H. pylori transcript abundance at acid pH. These studies document the complex response of H. pylori to environmental pH changes, and provide insight into mechanisms used for intragastric survival.
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Affiliation(s)
- Catherine C McGowan
- Division of Infectious Diseases, Department of Medicine, A-3310 Medical Center North, Vanderbilt University School of Medicine, Nashville, TN 37232-2605, USA.
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54
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Liu Z, Binns AN. Functional subsets of the virB type IV transport complex proteins involved in the capacity of Agrobacterium tumefaciens to serve as a recipient in virB-mediated conjugal transfer of plasmid RSF1010. J Bacteriol 2003; 185:3259-69. [PMID: 12754223 PMCID: PMC155385 DOI: 10.1128/jb.185.11.3259-3269.2003] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The virB-encoded type IV transport complex of Agrobacterium tumefaciens mediates the transfer of DNA and proteins into plant cells, as well as the conjugal transfer of IncQ plasmids, such as RSF1010, between Agrobacterium strains. While several studies have indicated that there are physical interactions among the 11 VirB proteins, the functional significance of the interactions has been difficult to establish since all of the proteins are required for substrate transfer. Our previous studies, however, indicated that although all of the VirB proteins are required for the capacity of a strain to serve as an RSF1010 donor, only a subset of these proteins in the recipient is necessary to increase the conjugal frequency by 3 to 4 logs. The roles of particular groups of VirB proteins in this increased recipient activity were examined in the study reported here. Examination of the expression of subgroups of virB genes revealed that translation of virB6 is necessary for expression of downstream open reading frames. Expression of limited subsets of the VirB proteins in a recipient strain lacking the Ti plasmid revealed that the VirB7 to VirB10 proteins yield a subcomplex that is functional in the recipient assay but that the VirB1 to VirB4 proteins, as a group, dramatically increase this activity in strains expressing VirB7 to VirB10. Finally, the membrane distribution and cross-linking patterns of VirB10, but not of VirB8 or VirB9, in a strain expressing only VirB7 to VirB10 are significantly altered compared to the patterns of the wild type. These characteristics are, however, restored to the wild-type status by coexpression of VirB1 to VirB3. Taken together, these results define subsets of type IV transport complex proteins that are critical in allowing a strain to participate as a recipient in virB-mediated conjugal RSF1010 transfer.
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Affiliation(s)
- Zhenying Liu
- Plant Science Institute, Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018, USA
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55
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Hofreuter D, Haas R. Characterization of two cryptic Helicobacter pylori plasmids: a putative source for horizontal gene transfer and gene shuffling. J Bacteriol 2002; 184:2755-66. [PMID: 11976306 PMCID: PMC135030 DOI: 10.1128/jb.184.10.2755-2766.2002] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Many Helicobacter pylori isolates carry cryptic plasmids of extremely variable size. In this study we analyzed two H. pylori plasmids, pHel4 and pHel5, from H. pylori strains P8 and P29, respectively. Plasmid pHel4 consists of 10,970 bp, constituting 15 putative open reading frames (ORFs), whereas pHel5 consists of 18,291 bp, constituting 17 ORFs. The findings that both plasmids encode a conserved RepA protein and that both have an origin of replication containing an iteron place them in the group of theta plasmids. In pHel4, the products of the overlapping orf4C, orf4D, orf4E, and orf4F sequences are homologous to MobA, MobB, MobC, and MobD, encoded by colicinogenic plasmids, suggesting that pHel4 might be mobilizable. A further putative operon consists of orf4B and orf4A, the products of which are homologous to microcin C7 (MccC7) biosynthesis and secretion proteins MccB and MccC, respectively. Plasmid pHel5 carries putative genes encoding proteins with homology to an endonuclease and gene products of an H. pylori chromosomal plasticity zone. Both plasmids contain repeat sequences, such as the previously identified R2 repeat, which are considered preferred recombination sites. In pHel4, a new repeat sequence (R4 repeat), which seems to act as a hot spot for site-specific recombination, was identified. All H. pylori plasmids characterized so far have a modular structure. We suggest a model that explains the existing plasmids by insertions and deletions of genetic elements at the repeat sequences. A genetic exchange between plasmids and the bacterial chromosome, combined with plasmid mobilization, might add a novel mechanism to explain the high genetic macrodiversity within the H. pylori population.
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Affiliation(s)
- Dirk Hofreuter
- Max von Pettenkofer Institut für Hygiene und Medizinische Mikrobiologie, Ludwig-Maximilians Universität München, Petterkoferstrasse 9A, D-80336 Munich, Germany
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56
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Smeets LC, Kusters JG. Natural transformation in Helicobacter pylori: DNA transport in an unexpected way. Trends Microbiol 2002; 10:159-62; discussion 162. [PMID: 11912014 DOI: 10.1016/s0966-842x(02)02314-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Like other bacterial species with a high frequency of inter-strain recombination, the human gastric pathogen Helicobacter pylori is competent for natural transformation. Recent data, however, indicate that its DNA-uptake system differs significantly from that in other species that contain DNA-uptake systems related to type IV pili. Instead, in H. pylori it has been suggested that the five proteins that form the transmembrane channel of the transformation system are closely related to subunits of type IV secretion systems.
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Affiliation(s)
- Leonard C Smeets
- Dept of Medical Microbiology and Infection Control, VU University Medical Center, PO box 7057, 1007 MB, Amsterdam, The Netherlands.
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57
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Friedrich A, Prust C, Hartsch T, Henne A, Averhoff B. Molecular analyses of the natural transformation machinery and identification of pilus structures in the extremely thermophilic bacterium Thermus thermophilus strain HB27. Appl Environ Microbiol 2002; 68:745-55. [PMID: 11823215 PMCID: PMC126729 DOI: 10.1128/aem.68.2.745-755.2002] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Thermus thermophilus HB27, an extremely thermophilic bacterium, exhibits high competence for natural transformation. To identify genes of the natural transformation machinery of T. thermophilus HB27, we performed homology searches in the partially completed T. thermophilus genomic sequence for conserved competence genes. These analyses resulted in the detection of 28 open reading frames (ORFs) exhibiting significant similarities to known competence proteins of gram-negative and gram-positive bacteria. Disruption of 15 selected potential competence genes led to the identification of 8 noncompetent mutants and one transformation-deficient mutant with a 100-fold reduced transformation frequency. One competence protein is similar to DprA of Haemophilus influenzae, seven are similar to type IV pilus proteins of Pseudomonas aeruginosa or Neisseria gonorrhoeae (PilM, PilN, PilO, PilQ, PilF, PilC, PilD), and another deduced protein (PilW) is similar to a protein of unknown function in Deinococcus radiodurans R1. Analysis of the piliation phenotype of T. thermophilus HB27 revealed the presence of single pilus structures on the surface of the wild-type cells, whereas the noncompetent pil mutants of Thermus, with the exception of the pilF mutant, were devoid of pilus structures. These results suggest that pili and natural transformation in T. thermophilus HB27 are functionally linked.
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Affiliation(s)
- Alexandra Friedrich
- Institut für Genetik und Mikrobiologie, Ludwig-Maximilians-Universität, Maria-Ward-Strasse 1a, D-80638 Münich, Germany
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58
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Guillemin KJ, Salama NR. Helicobacter pylori functional genomics. METHODS IN MICROBIOLOGY 2002. [DOI: 10.1016/s0580-9517(02)33017-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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59
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Chang KC, Yeh YC, Lin TL, Wang JT. Identification of genes associated with natural competence in Helicobacter pylori by transposon shuttle random mutagenesis. Biochem Biophys Res Commun 2001; 288:961-8. [PMID: 11689003 DOI: 10.1006/bbrc.2001.5877] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To identify genes involved in DNA transformation, we generated 1500 insertion mutants of a Helicobacter pylori strain by transposon shuttle mutagenesis. All mutant strains were screened for their frequency of natural transformation. A total of 20 mutant strains were found to exhibit a significantly decreased transformation frequency. DNA sequencing revealed seven genetic loci, including the reported comB locus, HP0017 (a putative virB4 homologue) and five loci without database match (HP0015, HP1089, HP1326, HP1424, and HP1473) from the 20 mutants. Reknockout of HP1326 revealed no impairment in natural transformation, while the other 5 mutants showed the same defective in natural transformation. Mutation of HP0017 severely impaired natural transformation both chromosome and plasmid DNA. Slot blot analysis revealed that some noncompetent strains had decreased virB4 RNA expression levels compared with competent strains. Nineteen ORFs had decreased expression levels in virB4 knockout mutant by microarray. Therefore, our data indicate that HP0017 is a virB4 homologue and is essential in the natural competence of H. pylori. HP0015, HP1089, HP1424, and HP1473 genes could be also involved in natural transformation.
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Affiliation(s)
- K C Chang
- Graduate Institute of Microbiology, National Taiwan University, College of Medicine, Taipei, Taiwan
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60
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Hofreuter D, Odenbreit S, Haas R. Natural transformation competence in Helicobacter pylori is mediated by the basic components of a type IV secretion system. Mol Microbiol 2001; 41:379-91. [PMID: 11489125 DOI: 10.1046/j.1365-2958.2001.02502.x] [Citation(s) in RCA: 170] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Helicobacter pylori (Hp), a Gram-negative bacterial pathogen and aetiologic agent of gastroduodenal disease in humans, is naturally competent for genetic transformation. Natural competence in bacteria is usually correlated with the presence of type IV pili or type IV pilin-like proteins, which are absent in Hp. Instead, we recently identified the comB operon in Hp, carrying four genes tentatively designated as orf2, comB1, comB2 and comB3. We show here that all ComB proteins and the 37-amino-acid Orf2 peptide display significant primary sequence and structural homology/identity to the basic components of a type IV secretion apparatus. ComB1, ComB2 and ComB3, now renamed ComB8, ComB9 and ComB10, correspond to the Agrobacterium tumefaciens VirB8, VirB9 and VirB10 proteins respectively. The peptide Orf2 carries a lipoprotein motif and a second cysteine residue homologous to VirB7, and was thus designated ComB7. The putative ATPase ComB4, encoded by the open reading frame hp0017 of strain 26695, corresponds to virB4 of the A. tumefaciens type IV secretion system. A Hp comB4 transposon insertion mutant was totally defective in natural transformation. By complementation of a Hp DeltacomB deletion mutant, we demonstrate that each of the proteins from ComB8 to ComB10 is absolutely essential for the development of natural transformation competence. The putative lipoprotein ComB7 is not essential, but apparently stabilizes the apparatus and modulates the transformation efficiency. Thus, pathogenic type I Hp strains contain two functional independent type IV transport systems, one for protein translocation encoded by the cag pathogenicity island and one for uptake of DNA by natural transformation. The latter system indicates a possible novel mechanism for natural DNA transformation in bacteria.
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Affiliation(s)
- D Hofreuter
- Max von Pettenkofer Institut für Hygiene und Medizinische Mikrobiologie, Pettenkoferstr. 9a, D-80336 München, Germany
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61
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Maggi Solcà N, Bernasconi MV, Valsangiacomo C, Van Doorn LJ, Piffaretti JC. Population genetics of Helicobacter pylori in the southern part of Switzerland analysed by sequencing of four housekeeping genes (atpD, glnA, scoB and recA), and by vacA, cagA, iceA and IS605 genotyping. MICROBIOLOGY (READING, ENGLAND) 2001; 147:1693-1707. [PMID: 11390701 DOI: 10.1099/00221287-147-6-1693] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The population biology of 78 Helicobacter pylori strains (71 from Swiss Italian, 4 from East Asian and 3 from South African patients) was investigated by sequence analysis of four housekeeping genes: atpD, scoB, glnA and recA. The vacA genotype, the presence of cagA and IS605, the iceA allelic type, and the resistance to metronidazole, clarithromycin and amoxycillin were determined. A high percentage of DNA polymorphic sites (19.8% for atpD, 21.3% for scoB, 23.7% for glnA and 20.3% for recA) was found. The phylogenetic trees based on the nucleotide sequences of the four gene fragments showed different topologies and were incongruent. The virulence-associated markers were distributed over the dendrograms and no association was found with phylogenetic clusters or clinical manifestations (chronic gastritis, gastric or duodenal ulcer, MALT lymphoma). Moreover, the H ratios (calculated with the homoplasy test) ranged from 0.742 to 0.799, depending on the gene fragment examined. All these observations suggest that H. pylori exists as a recombinant population. The clustering of the strains according to their geographical origin (USA/Europe, East Asia, South Africa) that has recently been demonstrated elsewhere could only be confirmed for the East Asian vacA s1c strains. In contrast, the South African strains clustered together only in the atpD tree. Presumably, recombination at the different loci has masked the evolutionary relationship among the strains.
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Affiliation(s)
- Nadia Maggi Solcà
- Istituto Cantonale Batteriosierologico, Via Ospedale 6, 6904 Lugano, Switzerland1
| | - Marco V Bernasconi
- Istituto Cantonale Batteriosierologico, Via Ospedale 6, 6904 Lugano, Switzerland1
| | | | - Leen-Jan Van Doorn
- Delft Diagnostic Laboratory, R. de Graafweg 7, 2625 AD Delft, The Netherlands2
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62
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Assmann IA, Enders GA, Püls J, Rieder G, Haas R, Hatz RA. Role of virulence factors, cell components and adhesion in Helicobacter pylori-mediated iNOS induction in murine macrophages. FEMS IMMUNOLOGY AND MEDICAL MICROBIOLOGY 2001; 30:133-8. [PMID: 11267846 DOI: 10.1111/j.1574-695x.2001.tb01561.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To investigate the mechanisms involved in Helicobacter pylori-mediated inducible nitric oxide synthase (iNOS) upregulation in mononuclear cells we cocultivated human THP-1 acute monocytic leukemia cells and murine J774A.1 professional macrophages with different H. pylori wild-type strains and mutants. We have shown that H. pylori-mediated iNOS induction in J774A.1 is independent of established virulence factors but dependent on direct interaction between bacteria and cells. In J774A.1, iNOS was equally upregulated by the wild-type strains J99, 26695, P12, and P1 as well as by mutants lacking the cag pathogenicity island, vacA, katA, alpAB genes and the hp0043 gene taking part in lipopolysaccharide biosynthesis when direct cell contact was allowed but not when bacteria and cells were separated by protein-permeable filter membranes. In contrast, iNOS was not induced in THP-1. This indicates that H. pylori-mediated iNOS induction in J774A.1 is independent of important virulence factors whereas cell contact is crucial which suggests a role of adhesion or phagocytosis.
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Affiliation(s)
- I A Assmann
- Department of Surgery, Klinikum Grosshadern, Ludwig-Maximilians-University Munich, Germany
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63
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Ando T, Xu Q, Torres M, Kusugami K, Israel DA, Blaser MJ. Restriction-modification system differences in Helicobacter pylori are a barrier to interstrain plasmid transfer. Mol Microbiol 2000; 37:1052-65. [PMID: 10972824 DOI: 10.1046/j.1365-2958.2000.02049.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Helicobacter pylori cells are naturally competent for the uptake of both plasmid and chromosomal DNA. However, we demonstrate that there are strong barriers to transformation of H. pylori strains by plasmids derived from unrelated strains. We sought to determine the molecular mechanisms underlying these barriers. Transformation efficiency was assessed using pHP1, an Escherichia coli-H. pylori shuttle vector conferring kanamycin resistance. Transformation of 33 H. pylori strains was attempted with pHP1 purified from either E. coli or H. pylori, and was successfully introduced into only 11 strains. Digestion of H. pylori chromosomes with different restriction endonucleases (REs) showed that DNA methylation patterns vary substantially among strains. The strain most easily transformed, JP26, was found to have extremely low endogenous RE activity and to lack a restriction-modification (R-M) system, homologous to MboI, which is highly conserved among H. pylori strains. When we introduced this system to JP26, pHP1 from MboI.M+ JP26, but not from wild-type JP26, transformed MboI R-M+ JP26 and heterologous MboI R-M+ wild-type H. pylori strains. Parallel studies with pHP1 from dam+ and dam- E. coli strains confirmed these findings. These data indicate that the endogenous REs of H. pylori strains represent a critical barrier to interstrain plasmid transfer among H. pylori.
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Affiliation(s)
- T Ando
- Division of Infectious Diseases, Department of Medicine, Vanderbilt University School of Medicine and VA Medical Center, Nashville, TN, USA
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64
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Bacon DJ, Alm RA, Burr DH, Hu L, Kopecko DJ, Ewing CP, Trust TJ, Guerry P. Involvement of a plasmid in virulence of Campylobacter jejuni 81-176. Infect Immun 2000; 68:4384-90. [PMID: 10899834 PMCID: PMC98329 DOI: 10.1128/iai.68.8.4384-4390.2000] [Citation(s) in RCA: 276] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Campylobacter jejuni strain 81-176 contains two, previously undescribed plasmids, each of which is approximately 35 kb in size. Although one of the plasmids, termed pTet, carries a tetO gene, conjugative transfer of tetracycline resistance to another strain of C. jejuni could not be demonstrated. Partial sequence analysis of the second plasmid, pVir, revealed the presence of four open reading frames which encode proteins with significant sequence similarity to Helicobacter pylori proteins, including one encoded by the cag pathogenicity island. All four of these plasmid-encoded proteins show some level of homology to components of type IV secretion systems. Mutation of one of these plasmid genes, comB3, reduced both adherence to and invasion of INT407 cells to approximately one-third that seen with wild-type strain 81-176. Mutation of comB3 also reduced the natural transformation frequency. A mutation in a second plasmid gene, a virB11 homolog, resulted in a 6-fold reduction in adherence and an 11-fold reduction in invasion compared to the wild type. The isogenic virB11 mutant of strain 81-176 also demonstrated significantly reduced virulence in the ferret diarrheal disease model. The virB11 homolog was detected on plasmids in 6 out of 58 fresh clinical isolates of C. jejuni, suggesting that plasmids are involved in the virulence of a subset of C. jejuni pathogens.
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Affiliation(s)
- D J Bacon
- Enteric Diseases Department, Naval Medical Research Center, Silver Spring, Maryland 20910, USA
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65
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Smeets LC, Bijlsma JJ, Boomkens SY, Vandenbroucke-Grauls CM, Kusters JG. comH, a novel gene essential for natural transformation of Helicobacter pylori. J Bacteriol 2000; 182:3948-54. [PMID: 10869072 PMCID: PMC94579 DOI: 10.1128/jb.182.14.3948-3954.2000] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2000] [Accepted: 04/26/2000] [Indexed: 11/20/2022] Open
Abstract
Helicobacter pylori is naturally competent for transformation, but the DNA uptake system of this bacterium is only partially characterized, and nothing is known about the regulation of competence in H. pylori. To identify other components involved in transformation or competence regulation in this species, we screened a mutant library for competence-deficient mutants. This resulted in the identification of a novel, Helicobacter-specific competence gene (comH) whose function is essential for transformation of H. pylori with chromosomal DNA fragments as well as with plasmids. Complementation of comH mutants in trans completely restored competence. Unlike other transformation genes of H. pylori, comH does not belong to a known family of orthologous genes. Moreover, no significant homologs of comH were identified in currently available databases of bacterial genome sequences. The comH gene codes for a protein with an N-terminal leader sequence and is present in both highly competent and less-efficient transforming H. pylori strains. A comH homolog was found in Helicobacter acinonychis but not in Helicobacter felis and Helicobacter mustelae.
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Affiliation(s)
- L C Smeets
- Department of Medical Microbiology and Infection Control, Vrije Universiteit, Amsterdam, The Netherlands
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66
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Hofreuter D, Odenbreit S, Püls J, Schwan D, Haas R. Genetic competence in Helicobacter pylori: mechanisms and biological implications. Res Microbiol 2000; 151:487-91. [PMID: 10961464 DOI: 10.1016/s0923-2508(00)00164-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Helicobacter pylori is naturally competent for genetic transformation. The comB locus, consisting of the open reading frames orf2, comB1, comB2, and comB3, is involved in natural transformation competence. Homologies of the ComB proteins with components of the type IV secretion apparatus (VirB9 and VirB10) from the Ti plasmid of Agrobacterium tumefaciens, as well as proteins involved in conjugation of plasmids RP1 and RP4, suggest a similar organization of DNA import (transformation) in H. pylori with well-known DNA export systems.
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Affiliation(s)
- D Hofreuter
- Max von Pettenkofer Institute for Hygiene and Medical Microbiology, Ludwig-Maximilians University, Munich, Germany
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67
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Abstract
For Helicobacter pylori, which exhibits substantial genetic diversity, many strains are naturally competent for transformation by exogenous DNA. To better understand the mechanism of natural transformation and its role in the generation of diversity, we sought to systematically identify factors important for natural transformation in H. pylori. We now show that the highest frequency of H. pylori transformation occurs when DNA is introduced prior to exponential phase growth, and that it is a saturable phenomenon. That transformation can be inhibited by DNA from Helicobacter (H. pylori and Helicobacter bilis) but not Escherichia coli suggests specificity based on DNA source. Finally, the cag island was determined to be unnecessary for high-frequency transformation.
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Affiliation(s)
- D A Israel
- Division of Infectious Diseases, Department of Medicine, Vanderbilt University School of Medicine and VA Medical Center, A-3310 Medical Center North, Nashville, TN 37232-2605, USA.
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68
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Smeets LC, Bijlsma JJ, Kuipers EJ, Vandenbroucke-Grauls CM, Kusters JG. The dprA gene is required for natural transformation of Helicobacter pylori. FEMS IMMUNOLOGY AND MEDICAL MICROBIOLOGY 2000; 27:99-102. [PMID: 10640603 DOI: 10.1111/j.1574-695x.2000.tb01418.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Genetic recombination in Helicobacter pylori is believed to be involved in host adaptation of this gastric pathogen and uptake of DNA by natural transformation can result in changes in virulence factors as well as antigenic variation. To elucidate the mechanisms involved in natural transformation we tested two genes with homology to known competence genes (dprA and traG) for their role in this process. Insertion mutants in these genes were constructed in two different H. pylori strains and their competence by natural transformation was compared to the wild-type. Mutation of the traG homolog did not reduce competence. Mutation of the dprA gene, however, severely impaired natural transformation both with plasmid and chromosomal DNA. Our data indicate that dprA and comB3 are essential parts of a common pathway for chromosomal and plasmid transformation.
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Affiliation(s)
- L C Smeets
- Department of Medical Microbiology, Faculty of Medicine, Vrije Universiteit Amsterdam, Van der Boechorststraat 7, 1081 BT, Amsterdam, The Netherlands
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69
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Ge Z, Taylor DE. Contributions of genome sequencing to understanding the biology of Helicobacter pylori. Annu Rev Microbiol 1999; 53:353-87. [PMID: 10547695 DOI: 10.1146/annurev.micro.53.1.353] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
About half of the world's population carries Helicobacter pylori, a gram-negative, spiral bacterium that colonizes the human stomach. The link between H. pylori and, ulceration as well as its association with the development of both gastric cancer and mucosa-associated lymphoid tissue lymphoma in humans is a serious public health concern. The publication of the genome sequences of two stains of H. pylori gives rise to direct evidence on the genetic diversity reported previously with respect to gene organization and nucleotide variability from strain to strain. The genome size of H. pylori strain 26695 is 1,6697,867 bp and is 1,643,831 bp for strain J99. Approximately 89% of the predicted open reading frames are common to both of the strains, confirming H. pylori as a single species. A region containing approximately 45% of H. pylori strain-specific open reading frames, termed the plasticity zone, is present on the chromosomes, verifying that some strain variability exists. Frequent alteration of nucleotides in the third position of the triplet codons and various copies of insertion elements on the individual chromosomes appear to contribute to distinct polymorphic fingerprints among strains analyzed by restriction fragment length polymorphisms, random amplified polymorphic DNA method, and repetitive element-polymerase chain reaction. Disordered chromosomal locations of some genes seen by pulsed-field gel electrophoresis are likely caused by rearrangement or inversion of certain segments in the genomes. Cloning and functional characterization of the genes involved in acidic survival, vacuolating toxin, cag-pathogenicity island, motility, attachment to epithelial cells, natural transformation, and the biosynthesis of lipopolysaccharides have considerably increased our understanding of the molecular genetic basis for the pathogenesis of H. pylori. The homopolymeric nucleotide tracts and dinucleotide repeats, which potentially regulate the on- and off-status of the target genes by the strand-slipped mispairing mechanism, are often found in the genes encoding the outer-membrane proteins, in enzymes for lipopolysaccharide synthesis, and within DNA modification/restriction systems. Therefore, these genes may be involved in the H. pylori-host interaction.
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Affiliation(s)
- Z Ge
- Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge 02139, USA
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70
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Doig P, de Jonge BL, Alm RA, Brown ED, Uria-Nickelsen M, Noonan B, Mills SD, Tummino P, Carmel G, Guild BC, Moir DT, Vovis GF, Trust TJ. Helicobacter pylori physiology predicted from genomic comparison of two strains. Microbiol Mol Biol Rev 1999; 63:675-707. [PMID: 10477312 PMCID: PMC103750 DOI: 10.1128/mmbr.63.3.675-707.1999] [Citation(s) in RCA: 146] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Helicobacter pylori is a gram-negative bacteria which colonizes the gastric mucosa of humans and is implicated in a wide range of gastroduodenal diseases. This paper reviews the physiology of this bacterium as predicted from the sequenced genomes of two unrelated strains and reconciles these predictions with the literature. In general, the predicted capabilities are in good agreement with reported experimental observations. H. pylori is limited in carbohydrate utilization and will use amino acids, for which it has transporter systems, as sources of carbon. Energy can be generated by fermentation, and the bacterium possesses components necessary for both aerobic and anaerobic respiration. Sulfur metabolism is limited, whereas nitrogen metabolism is extensive. There is active uptake of DNA via transformation and ample restriction-modification activities. The cell contains numerous outer membrane proteins, some of which are porins or involved in iron uptake. Some of these outer membrane proteins and the lipopolysaccharide may be regulated by a slipped-strand repair mechanism which probably results in phase variation and plays a role in colonization. In contrast to a commonly held belief that H. pylori is a very diverse species, few differences were predicted in the physiology of these two unrelated strains, indicating that host and environmental factors probably play a significant role in the outcome of H. pylori-related disease.
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Affiliation(s)
- P Doig
- AstraZeneca R&D Boston, Cambridge, Massachusetts 02139, USA.
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71
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Marais A, Mendz GL, Hazell SL, Mégraud F. Metabolism and genetics of Helicobacter pylori: the genome era. Microbiol Mol Biol Rev 1999; 63:642-74. [PMID: 10477311 PMCID: PMC103749 DOI: 10.1128/mmbr.63.3.642-674.1999] [Citation(s) in RCA: 157] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The publication of the complete sequence of Helicobacter pylori 26695 in 1997 and more recently that of strain J99 has provided new insight into the biology of this organism. In this review, we attempt to analyze and interpret the information provided by sequence annotations and to compare these data with those provided by experimental analyses. After a brief description of the general features of the genomes of the two sequenced strains, the principal metabolic pathways are analyzed. In particular, the enzymes encoded by H. pylori involved in fermentative and oxidative metabolism, lipopolysaccharide biosynthesis, nucleotide biosynthesis, aerobic and anaerobic respiration, and iron and nitrogen assimilation are described, and the areas of controversy between the experimental data and those provided by the sequence annotation are discussed. The role of urease, particularly in pH homeostasis, and other specialized mechanisms developed by the bacterium to maintain its internal pH are also considered. The replicational, transcriptional, and translational apparatuses are reviewed, as is the regulatory network. The numerous findings on the metabolism of the bacteria and the paucity of gene expression regulation systems are indicative of the high level of adaptation to the human gastric environment. Arguments in favor of the diversity of H. pylori and molecular data reflecting possible mechanisms involved in this diversity are presented. Finally, we compare the numerous experimental data on the colonization factors and those provided from the genome sequence annotation, in particular for genes involved in motility and adherence of the bacterium to the gastric tissue.
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Affiliation(s)
- A Marais
- Laboratoire de Bactériologie, Université Victor Segalen Bordeaux 2, 33076 Bordeaux Cedex, France
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72
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Ando T, Israel DA, Kusugami K, Blaser MJ. HP0333, a member of the dprA family, is involved in natural transformation in Helicobacter pylori. J Bacteriol 1999; 181:5572-80. [PMID: 10482496 PMCID: PMC94075 DOI: 10.1128/jb.181.18.5572-5580.1999] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/1999] [Accepted: 06/25/1999] [Indexed: 11/20/2022] Open
Abstract
Helicobacter pylori is naturally competent for DNA transformation, but the mechanism by which transformation occurs is not known. For Haemophilus influenzae, dprA is required for transformation by chromosomal but not plasmid DNA, and the complete genomic sequence of H. pylori 26695 revealed a dprA homolog (HP0333). Examination of genetic databases indicates that DprA homologs are present in a wide variety of bacterial species. To examine whether HP0333 has a function similar to dprA of H. influenzae, HP0333, present in each of 11 strains studied, was disrupted in two H. pylori isolates. For both mutants, the frequency of transformation by H. pylori chromosomal DNA was markedly reduced, but not eliminated, compared to their wild-type parental strains. Mutation of HP0333 also resulted in a marked decrease in transformation frequency by a shuttle plasmid (pHP1), which differs from the phenotype described in H. influenzae. Complementation of the mutant with HP0333 inserted in trans in the chromosomal ureAB locus completely restored the frequency of transformation to that of the wild-type strain. Thus, while dprA is required for high-frequency transformation, transformation also may occur independently of DprA. The presence of DprA homologs in bacteria known not to be naturally competent suggests a broad function in DNA processing.
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Affiliation(s)
- T Ando
- Division of Infectious Diseases, Department of Medicine, Vanderbilt University School of Medicine and VA Medical Center, Nashville, Tennessee, USA
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73
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Li PL, Hwang I, Miyagi H, True H, Farrand SK. Essential components of the Ti plasmid trb system, a type IV macromolecular transporter. J Bacteriol 1999; 181:5033-41. [PMID: 10438776 PMCID: PMC93993 DOI: 10.1128/jb.181.16.5033-5041.1999] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The trb operon from pTiC58 is one of three loci that are required for conjugal transfer of this Ti plasmid. The operon, which probably codes for the mating bridge responsible for pair formation and DNA transfer, contains 12 genes, 11 of which are related to genes from other members of the type IV secretion system family. The 12th gene, traI, codes for production of Agrobacterium autoinducer (AAI). Insertion mutations were constructed in each of the 12 genes, contained on a full-length clone of the trb region, using antibiotic resistance cassettes or a newly constructed transposon. This transposon, called mini-Tn5Ptrb, was designed to express genes downstream of the insertion site from a promoter regulated by TraR and AAI. Each mutation could trans complement downstream Tn3HoHo1 insertions in the trb operon of full-sized Ti plasmids. When marker-exchanged into the transfer-constitutive Ti plasmid pTiC58DeltaaccR mutations in trbB, -C, -D, -E, -L, -F, -G, and -H abolished conjugal transfer from strain UIA5, which lacks the 450-kb catabolic plasmid pAtC58. However, these mutants retained residual conjugal transfer activity when tested in strain NT1, which contains this large plasmid. The trbJ mutant failed to transfer at a detectable frequency from either strain, while the trbI mutant transferred at very low but detectable levels from both donors. Only the trbK mutant was unaffected in conjugal transfer from either donor. Transfer of each of the marker-exchange mutants was restored by a clone expressing only the wild-type allele of the corresponding mutant trb gene. An insertion mutation in traI abolished the production of AAI and also conjugal transfer. This defect was restored by culturing the mutant donor in the presence of AAI. We conclude that all of the trb genes except trbI and trbK are essential for conjugal transfer of pTiC58. We also conclude that mutations in any one of the trb genes except traI and trbJ can be complemented by functions coded for by pAtC58.
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Affiliation(s)
- P L Li
- Departments of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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74
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Dang TA, Zhou XR, Graf B, Christie PJ. Dimerization of the Agrobacterium tumefaciens VirB4 ATPase and the effect of ATP-binding cassette mutations on the assembly and function of the T-DNA transporter. Mol Microbiol 1999; 32:1239-53. [PMID: 10383764 PMCID: PMC3918219 DOI: 10.1046/j.1365-2958.1999.01436.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The Agrobacterium tumefaciens VirB4 ATPase functions with other VirB proteins to export T-DNA to susceptible plant cells and other DNA substrates to a variety of prokaryotic and eukaryotic cells. Previous studies have demonstrated that VirB4 mutants with defects in the Walker A nucleotide-binding motif are non-functional and exert a dominant negative phenotype when synthesized in wild-type cells. This study characterized the oligomeric structure of VirB4 and examined the effects of Walker A sequence mutations on complex formation and transporter activity. VirB4 directed dimer formation when fused to the amino-terminal portion of cI repressor protein, as shown by immunity of Escherichia coli cells to lambda phage infection. VirB4 also dimerized in Agrobacterium tumefaciens, as demonstrated by the recovery of a detergent-resistant complex of native protein and a functional, histidine-tagged derivative by precipitation with anti-His6 antibodies and by Co2+ affinity chromatography. Walker A sequence mutants directed repressor dimerization in E. coli and interacted with His-VirB4 in A. tumefaciens, indicating that ATP binding is not required for self-association. A dimerization domain was localized to a proposed N-terminal membrane-spanning region of VirB4, as shown by the dominance of an allele coding for the N-terminal 312 residues and phage immunity of host cells expressing cI repressor fusions to alleles for the first 237 or 312 residues. A recent study reported that the synthesis of a subset of VirB proteins, including VirB4, in agrobacterial recipients has a pronounced stimulatory effect on the virB-dependent conjugal transfer of plasmid RSF1010 by agrobacterial donors. VirB4'312 suppressed the stimulatory effect of VirB proteins for DNA uptake when synthesized in recipient cells. In striking contrast, Walker A sequence mutants contributed to the stimulatory effect of VirB proteins to the same extent as native VirB4. These findings indicate that the oligomeric structure of VirB4, but not its capacity to bind ATP, is important for the assembly of VirB proteins as a DNA uptake system. The results of these studies support a model in which VirB4 dimers or homomultimers contribute structural information for the assembly of a transenvelope channel competent for bidirectional DNA transfer, whereas an ATP-dependent activity is required for configuring this channel as a dedicated export machine.
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75
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Marshall DG, Dundon WG, Beesley SM, Smyth CJ. Helicobacter pylori--a conundrum of genetic diversity. MICROBIOLOGY (READING, ENGLAND) 1998; 144 ( Pt 11):2925-2939. [PMID: 9846728 DOI: 10.1099/00221287-144-11-2925] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- David G Marshall
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, University of Dublin, Dublin 2, Republic of Ireland
| | - William G Dundon
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, University of Dublin, Dublin 2, Republic of Ireland
| | - Sarah M Beesley
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, University of Dublin, Dublin 2, Republic of Ireland
| | - Cyril J Smyth
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, University of Dublin, Dublin 2, Republic of Ireland
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76
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McGowan CC, Necheva A, Thompson SA, Cover TL, Blaser MJ. Acid-induced expression of an LPS-associated gene in Helicobacter pylori. Mol Microbiol 1998; 30:19-31. [PMID: 9786182 DOI: 10.1046/j.1365-2958.1998.t01-1-01079.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
To investigate urease-independent mechanisms by which Helicobacter pylori resists acid stress, subtractive RNA hybridization was used to identify H. pylori genes whose expression is induced after exposure to acid pH. This approach led to the isolation of a gene that encoded a predicted 34.8kDa protein (WbcJ), which was homologous to known bacterial O-antigen biosynthesis proteins involved in the conversion of GDP-mannose to GDP-fucose. An isogenic wbcJ null mutant strain failed to express O-antigen and Lewis X or Lewis Y determinants and was more sensitive to acid stress than was the wild-type strain. Qualitative differences in LPS profiles were observed in H. pylori cells grown at pH 5 compared with pH 7, which suggests that H. pylori may alter its LPS structure in response to acidic pH. This may be an important adaptation facilitating H. pylori colonization of the acidic gastric environment.
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Affiliation(s)
- C C McGowan
- Department of Medicine, Vanderbilt University Medical School, and Department of Veterans Affairs Medical Center, Nashville, TN, USA.
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