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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of the first two genes of the CS1 fimbrial operon in human enterotoxigenic Escherichia coli of serotype 0139: H28 (1991)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 80 (1991), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: An oligonucleotide, derived from the N-terminal amino acid sequence of the CS1 fimbrial sub-unit protein was used to identify the subunit gene on recombinant plasmid pDEP23 containing the structural genes of the CS1 fimbrial operon. The nucleotide sequence of the subunit gene (csoA), encoding a protein of 171 amino acids, was determined. Flanking it upstream, a gene (csoB) encoding a protein of 238 amino acids was found. The CsoB and CsoA protein are homologous to the CfaA and CfaB proteins in the CFA/I fimbrial operon. For all the CS1 producing strains investigated the structural genes are located on plasmids. Like CFA/I fimbriae, CS1 fimbriae are only expressed in the presence of a positive regulator, CfaD for CFA/I and Rns for CS1, respectively. The promoter region upstream of the csoB gene was cloned in front of the promoterless alkaline phosphatase (phoA) gene of the promoter-probe vector pCB267. PhoA activity was enhanced approximately two-fold by the introduction of compatible plasmids containing either rns or cfaD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1991.tb04673.x
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  • 2
    Electronic Resource
    Electronic Resource
    The iron-responsive regulator Fur of Campylobacter jejuni is expressed from two separate promoters (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 188 (2000), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A lacZ-based reporter gene system was used to identify the promoter of the Campylobacter jejuni iron-responsive gene regulator Fur. In other Gram-negative bacteria, the fur promoter is usually located directly upstream of the fur gene and is often autoregulated in response to iron. In this study we demonstrate that expression of the C. jejuni fur gene is controlled from two promoters located in front of the first and second open reading frames upstream of fur. Neither of these promoters was iron-regulated, and the presence of both promoters in front of fur gives higher expression of the lacZ reporter than with either promoter alone. Expression from two distal promoters might be a mechanism for regulating the level of the C. jejuni Fur protein in response to unknown stimuli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2000.tb09180.x
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  • 3
    Electronic Resource
    Electronic Resource
    Transcriptional and mutational analysis of the Helicobacter pylori urease promoter (2002)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 213 (2002), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Urease is an essential virulence factor of the human gastric pathogen Helicobacter pylori, and is expressed to very high levels. The promoter of the urease operon contains sequences resembling the canonical −10 and extended −10 motifs, but no discernible −35 motif. To establish the role of different motifs and regions in the urease promoter, we fused the urease promoter to a genomic lacZ reporter gene in H. pylori, made substitutions in the aforementioned promoter motifs, and also made deletions in the upstream sequences removing regulatory sequences. Substitutions in the −10, extended −10 and predicted −35 motifs all significantly altered expression of the lacZ reporter gene, demonstrating their importance in transcription of the H. pylori urease operon. In contrast, sequential deletions upstream of the −35 region did not affect expression of the lacZ reporter gene. This demonstrates the modular structure of the H. pylori urease promoter, where basal levels of transcription are initiated from a typical σ70 promoter, which requires −10 and extended −10 motifs, and also its −35 motif for efficient transcription. Upstream sequences are not involved in basal levels of urease transcription, but play an important role in responses to environmental stimuli like nickel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2002.tb11281.x
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  • 4
    Electronic Resource
    Electronic Resource
    Identification of iron-regulated genes of Helicobacter pylori by a modified Fur titration assay (FURTA-Hp) (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 184 (2000), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The Escherichia coli-based Fur titration assay (FURTA), although a powerful tool for identification of genes regulated by the ferric uptake regulator (Fur), was unsuccessful for the gastric pathogen Helicobacter pylori. The FURTA was modified by construction of an E. coli indicator strain producing H. pylori Fur only. The promoter regions of the ferric citrate receptor homolog fecA2 and the riboflavin synthesis gene ribBA were both positive in the modified FURTA, but negative in the original FURTA. Transcription of fecA2 and ribBA was demonstrated to be iron-repressed in H. pylori. This type of modification should allow FURTA analysis for bacteria with Fur binding sequences poorly recognized by E. coli Fur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2000.tb09018.x
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  • 5
    Electronic Resource
    Electronic Resource
    The role of Helicobacter pylori virulence factors in interleukin production by monocytic cells (2001)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 196 (2001), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Helicobacter pylori infection results in chronic gastritis, which is initiated by the release of cytokines like interleukin (IL)-12 and IL-8 from mononuclear cells, and IL-8 from gastric epithelial cells. The severity of gastritis is influenced both by host factors and by bacterial factors such as the Cag proteins and the vacuolating cytotoxin VacA. Amounts of IL-12 and IL-8 produced by monocytic THP-1 cells differed considerably between the eight H. pylori isolates tested, but in contrast to H. pylori-induced IL-8 production by gastric epithelial cells, did not correlate to the Cag and VacA types of the strains. Apparently, in addition to Cag and VacA, other bacterial factors determine the extent in which H. pylori induced IL production in monocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2001.tb10570.x
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  • 6
    Electronic Resource
    Electronic Resource
    The iron-induced ferredoxin FdxA of Campylobacter jejuni is involved in aerotolerance (2001)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 196 (2001), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A gene encoding a putative 2[4Fe–4S] ferredoxin (FdxA) was identified upstream of, and divergent to the peroxide stress defense gene ahpC of the microaerophilic pathogen Campylobacter jejuni. The transcription start site of fdxA was located 27 and 28 bp upstream of the fdxA start codon. Transcriptional fusions of the fdxA promoter to a lacZ reporter gene demonstrated that expression of fdxA is iron-induced, and thus oppositely regulated to the iron-repressed ahpC gene. Insertional mutagenesis of the fdxA gene did not affect microaerobic growth of C. jejuni, but significantly reduced aerotolerance of C. jejuni. The fdxA gene is the first reported iron-induced gene of C. jejuni, and encodes a novel component of its oxidative stress defense.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2001.tb10563.x
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  • 7
    Electronic Resource
    Electronic Resource
    The Functional Status of the Helicobacter pylori sabB Adhesin Gene as a Putative Marker for Disease Outcome (2004)
    Oxford, UK : Blackwell Science Ltd
    Helicobacter 9 (2004), S. 0 
    Details
    ISSN: 1523-5378
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background.  Helicobacter pylori factors that contribute to disease outcome are largely unknown, but intimate contact with host cells mediated by outer membrane proteins is thought to play an important role. Expression of the outer membrane proteins OipA, HopZ, SabA, and SabB is regulated by phase-variable dinucleotide repeats in the coding regions of the respective genes. We have evaluated the correlation between the expression status of these four genes and disease outcome of H. pylori infection in a Dutch patient population.Materials and Methods.  H. pylori strains, isolated from 96 Dutch patients with gastritis (n = 29), duodenal ulcer (n = 28), gastric ulcer (n = 21), gastric carcinoma (n = 9), and lymphoma (n = 9), were analyzed for the ‘on/off’ expression status of the H. pylori genes oipA, hopZ, sabA, and sabB by direct DNA sequence analysis of amplified fragments.Results.  The off-status of sabB was significantly associated with duodenal ulcer (p = .036), but not with gastric ulcer. In contrast, the expression status of oipA, hopZ, and sabA did not correlate with disease outcome. Furthermore, lymphoma strains appeared to express a significantly smaller amount of putative adhesins when compared to gastritis, gastric ulcer, duodenal ulcer and gastric carcinoma strains (p 〈 .02 for all groups tested).Conclusion.  The off-status of sabB was found to be associated with duodenal ulcer disease, and thus represents a putative marker for disease outcome. Assuming that SabB is involved in bacterial adhesion, this association suggests that adherent H. pylori are more prone to elimination by the host immune system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1083-4389.2004.00213.x
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  • 8
    Electronic Resource
    Electronic Resource
    Induced Helicobacter pylori vacuolating cytotoxin VacA expression after initial colonisation of human gastric epithelial cells (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 39 (2003), S. 0 
    Details
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: To study the effect of initial colonisation on Helicobacter pylori gene expression, altered H. pylori gene transcription during co-culture with human gastric epithelial cells was determined. Therefore, an insertion library of H. pylori with random chromosomal fusions to a promoterless cat gene was grown in the presence of HM02 gastric epithelial cells and varying levels of chloramphenicol. One H. pylori transformant was chloramphenicol-resistant in the presence, but chloramphenicol-susceptible in the absence of gastric epithelial HM02 cells. This transformant had the promoterless cat gene inserted into the HP0887 gene, which encodes the vacuolating cytotoxin VacA, an important virulence factor of H. pylori. Reverse transcriptase polymerase chain reaction on cDNA of this transformant confirmed vacA upregulation near HM02 cells. These results show the applicability of this technique to study H. pylori gene regulation in its natural environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0928-8244(03)00226-8
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  • 9
    Electronic Resource
    Electronic Resource
    The stress-induced hsp12 gene shows genetic variation among Helicobacter pylori strains (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 38 (2003), S. 0 
    Details
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The transcriptional regulation, genetic variation and clinical relevance of the strain-specific hsp12 gene of the human gastric pathogen Helicobacter pylori were investigated. Although the transcription of the hsp12 gene in H. pylori strain 1061 was induced by growth under iron-, pH- and temperature-stress conditions, the gene was not essential for growth under these stress conditions. The locus containing the hsp12 gene showed considerable genetic variation. A total of eight different strain-specific alleles were identified, of which three are mosaic variants of the hsp12 gene and five that are unrelated to the hsp12 gene. The hsp12 locus of six paired sets of strains obtained from patients with 7–10-year time intervals remained unaltered, indicating that genetic variation does not occur during chronic infection. No significant association was found between the presence of a hsp12 gene and peptic ulcer disease in clinical isolates obtained from 26 patients. The stress-regulated, strain-specific hsp12 genes may be involved in adaptation of individual H. pylori strains to their specific hosts, and contribute to long-term colonization of the gastric niche.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0928-8244(03)00105-6
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  • 10
    Electronic Resource
    Electronic Resource
    Restriction of DNA encoding selectable markers decreases the transformation efficiency of Helicobacter pylori (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 44 (2005), S. 0 
    Details
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Helicobacter pylori populations recovered from the human stomach display extensive recombination and quasispecies development, and this suggests frequent exchange of DNA between different strains in vivo. In vitro, however, most H. pylori strains display restriction to the uptake of non-self DNA, as measured using selectable markers, regardless of their competency for transformation with self DNA. We have examined the effect of different selectable markers on double-crossover recombination efficiencies in three reference strains (1061, 26695 & SS1) and one clinical isolate (CHP1) of H. pylori. All strains were efficiently transformable to kanamycin or chloramphenicol resistance by using self-genomic DNA from isogenic mutants bearing the aphA3 or cat cassettes, respectively. However, strains 26695 and CHP1 showed a 3–5-log reduction in transformation efficiency by non-self recombinant DNA containing aphA3, when compared to cat. Strain 1061 readily accepted either cassette, and strain SS1 was poorly tolerant of any non-self DNA. Genome-wide random mutagenesis of these strains was only achievable with a selectable marker that allowed high transformation efficiency. Digestion of 32P-labelled cassettes by H. pylori lysates mirrored the transformation results and indicated that in some strains these cassettes are the targets of enzymatic restriction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsim.2004.10.019
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