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  • 1
    Electronic Resource
    Electronic Resource
    Hemin-dependent growth and hemin binding of Bartonella henselae (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 189 (2000), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Bartonella henselae causes cat-scratch disease and bacillary angiomatosis peliosis. The bacteria reside in erythrocytes of asymptomatic cats, which represent the natural reservoir for this pathogen. B. henselae is usually grown on blood-enriched media. Growth experiments on Brucella medium without blood demonstrated that heme compounds are essential for the growth of B. henselae and can completely substitute the addition of blood components. The heme precursor protoporphyrin IX alone, or in combination with FeCl2 or FeCl3, as well as transferrin or lactoferrin did not support growth, indicating that B. henselae cannot synthesize heme itself. Hemin supported growth even when free iron was chelated, indicating that hemin is also used as an iron source. Binding assays showed that hemin starvation increased the binding capacity of B. henselae for hemin, providing evidence that the bacteria carry a specific hemin uptake system, which might be regulated by hemin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2000.tb09205.x
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  • 2
    Electronic Resource
    Electronic Resource
    Identification and molecular analysis of superoxide dismutase isoforms in Helicobacter pylori (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 183 (2000), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Three electromorphs of iron superoxide dismutase (FeSOD) were identified among 29 Helicobacter pylori isolates by native gel electrophoresis and activity staining. The electromorphs designated isoforms A, B, and C are characterized by slow, intermediate and fast electrophoretic migration, respectively, which was not observed under denaturing conditions. The isoforms were not associated with virulence determinants and with the outcome of disease. Sequence analysis of the sodB gene in strains producing different FeSOD isoforms and comparison of deduced protein sequences revealed that differences in the electric migration behavior are associated with exchange of charged amino acids, suggesting that faster migration is caused by a more negative total charge of the proteins. Electrophoretic migration of native FeSOD was not influenced by changes in the iron cofactor concentration, oxidative stress, and different media, indicating that FeSOD isoforms represent stable strain-specific markers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2000.tb08965.x
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  • 3
    Electronic Resource
    Electronic Resource
    Structural and functional analysis of the riboflavin synthesis genes encoding GTP cyclohydrolase II (ribA), DHBP synthase (ribBA), riboflavin synthase (ribC), and riboflavin deaminase/reductase (ribD) from Helicobacter pylori strain P1 (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 191 (2000), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The functions of the riboflavin synthesis gene homologues ribA, ribBA, ribC, and ribD from Helicobacter pylori strain P1 were confirmed by complementation of defined Escherichia coli mutant strains. The H. pylori ribBA gene, which is similar to bifunctional ribBA genes of Gram-positive bacteria, fully complemented the ribB mutation and partially restored growth in a ribC mutant. However, ribBA did not complement the ribA mutation in E. coli, thus explaining the presence of the additional separate copy of the ribA gene in the H. pylori chromosome. In E. coli exclusively ribA conferred hemolytic activity and gave rise to production of molecules with fluorescence characteristics similar to flavins, as observed earlier. The E. coli hemolysin ClyA was not involved in causing the hemolytic phenotype. No riboflavin synthesis genes on plasmids conferred iron uptake functions to a siderophore-deficient mutant of E. coli. Marker exchange mutagenesis of the genes in H. pylori was not successful indicating that riboflavin synthesis is essential for basic metabolic functions of the gastric pathogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2000.tb09339.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
    Cloning and characterization of the fur gene from Helicobacter pylori (1998)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 159 (1998), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The fur homologue of Helicobacter pylori was isolated by screening a plasmid-based, genomic DNA library using the Fur titration assay (FURTA). The analysis of the DNA sequence revealed significant homology with Fur proteins from various other bacterial species. The highest degree of homology was observed for the Fur protein from Campylobacter jejuni. The H. pylori fur gene on a plasmid could partially complement the fur mutation in Escherichia coli strain H1681. The repressor activity depended on addition of iron to the medium indicating that iron acts as a co-repressor for the H. pylori protein similar to Fur from other bacteria. Comparison of Fur from H. pylori strain NCTC11638 with the recently published genomic DNA sequence of another strain (26695) confirmed the identity of the fur homologue and revealed that the fur locus is highly conserved in both strains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1998.tb12860.x
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  • 7
    Electronic Resource
    Electronic Resource
    Mutational analysis of the Helicobacter pylori carbonic anhydrases (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: In the gastric microenvironment, Helicobacter pylori is exposed to bicarbonate, urea and acid. Here it is demonstrated that both H. pylori carbonic anhydrases (CAs) are required for maintaining urease activity and therefore influence H. pylori urea resistance at neutral pH. Furthermore, the β-CA is required for acid resistance as indicated by a growth defect of the corresponding mutant at low pH. The α- and β-CA mutants as well as the double mutant were more resistant to bicarbonate, indicating that both enzymes are involved in bicarbonate metabolism. These phenotypes support important CA-functions in H. pylori urea and bicarbonate metabolism and acid resistance. Thus, both CA enzymes might be required for survival in the gastric niche.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsim.2004.10.021
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  • 8
    Electronic Resource
    Electronic Resource
    Susceptibility in vitro of Helicobacter pylori to cetylpyridinium chloride (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 24 (1999), S. 0 
    Details
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The antimicrobial agent cetylpyridinium chloride (CPC) which is used in therapy of oro-pharyngeal infections and for antiseptic treatment of the oral cavity is active against different bacterial species. Determination of the minimal inhibitory concentration (MIC) using the agar dilution technique revealed that the gastric pathogen Helicobacter pylori in vitro is highly susceptible to CPC as indicated by an MIC of 10 μM (3.4 μg ml−1) which was significantly lower than the MIC of CPC against other bacterial species, which were analyzed in comparison to H. pylori. Bacteria of the genus Campylobacter, various Streptococcus spp., Staphylococcus aureus and Escherichia coli showed higher MICs ranging from 100 μM to 2 mM. In summary, this finding renders CPC-containing drugs candidates possibly useful for eradication or for the prevention of transmission of the gastric pathogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-695X.1999.tb01281.x
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  • 9
    Electronic Resource
    Electronic Resource
    Novel plasmids for gene expression analysis and for genetic manipulation in the gastric pathogen 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: To facilitate gene expression analysis in the human gastric pathogen Helicobacter pylori, we constructed the plasmids pHPLAC-KAN and pHPLAC-CAT containing a promoterless Escherichia coli lacZ gene located upstream from the antibiotic resistance genes aphA-3 or cat, respectively. The suitability of the plasmids for H. pylori mutagenesis and gene expression analysis was evaluated by plasmid integration into the genome of H. pylori strain 1061 by single homologous recombination, using the rpl9 gene encoding ribosomal protein L9 as target. By monitoring β-galactosidase production from the resulting rpl9::lacZ fusion, it was demonstrated that H. pylori rpl9 displays the classical growth phase-dependent regulation of components of the protein synthesis machinery, as β-galactosidase production dropped fivefold in the stationary growth phase. The plasmids described in this study extend our methodological repertoire for genetic modification and molecular analysis of H. pylori, and may also be of use for other bacteria, as the resistance cassettes and the lacZ gene are active in the related Campylobacter species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsim.2004.10.016
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  • 10
    Electronic Resource
    Electronic Resource
    Analysis of the rdxA gene in high-level metronidazole-resistant clinical isolates confirms a limited use of rdxA mutations as a marker for prediction of metronidazole resistance in Helicobacter pylori (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 36 (2003), S. 0 
    Details
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Metronidazole (Mtz) resistance in the gastric pathogen Helicobacter pylori is closely associated with inactivation of the nitroreductase gene rdxA. In order to identify respective mutations for diagnostic purposes we analyzed the rdxA gene in a collection of high-level Mtz-resistant clinical H. pylori isolates. Size alterations in the rdxA gene region were found in only two out of 45 and one out of 40 isolates showing lower-level (minimal inhibitory concentrations (MICs) 32–192 μg ml−1) and high-level (MIC≥256μg ml−1) Mtz resistance, respectively. Point mutations that interrupt the rdxA reading frame were detected in two out of eight high-level resistant isolates (MICs≥256μg ml−1). Most remarkably, the rdxA gene sequence was found to be identical in four out of five high-level Mtz-resistant and -susceptible paired H. pylori isolates from the same patients each. Taken together, these results demonstrate that although some isolates carry classical resistance-associated rdxA mutations, as described earlier, the use of rdxA mutations as a marker for prediction of Mtz resistance is limited.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0928-8244(03)00031-2
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