title: Acid-tolerance response in Helicobacter pylori and differences between cagA+ and cagA- strains.
abstract: Helicobacter pylori cagA transcription and translation are maximal at pH 6 in stationary phase. The aim of this study was to determine whether H. pylori has an acid-tolerance response and whether that response is related to CagA expression, by investigating whether preexposure to pH 5 or 6 improved survival of cells subsequently exposed to pH 3. Cell number was determined after broth growth, after exposure to pH 5, 6, or 7, and then after a 30-min exposure to pH 3 without urea. H. pylori cells preexposed to pH 6 or 5 survived pH 3 exposure 100-fold better than did cells preexposed to pH 7. Cells of cagA+ strains grown at pH 6 for 48 h, which induced maximal CagA expression, were significantly more susceptible to pH 3 than were wild type cagA- strains or isogenic cagA- knockouts. Thus, H. pylori strains possess a urea-independent acid-tolerance response. Differential acid susceptibility may contribute to preferential colonization of particular H. pylori strains in specific mucus layer niches.
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, VA Medical Center, Nashville, Tennessee 37232-2605, USA.
authors.forename: M
authors.initials: M
authors.lastname: Karita
authors.forename: M J
authors.initials: MJ
authors.lastname: Blaser
mesh_terms: D000942:Antigens, Bacterial; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D015169:Colony Count, Microbial; D016480:Helicobacter pylori / Q000235:genetics / Q000254:growth & development*; D006801:Humans; D006863:Hydrogen-Ion Concentration
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C080866:cagA protein, Helicobacter pylori