title: Characterization of the arginine decarboxylase gene (ORF HP0422, speA) involved in acid tolerance in Helicobacter pylori.
abstract: BACKGROUND
  Helicobacter pylori is a motile microaerophilic bacterium that colonizes the human stomach. H. pylori infection triggers gastric diseases, such as gastritis, peptic ulcer and gastric cancer. Stomach represents a barrier for microorganism colonization, particularly because of its high hydrochloric acid concentration. The main mechanism developed by H. pylori to maintain intracellular pH homeostasis in this environment is the urease activity. However, urease negative strains can be also isolated from clinical samples, suggesting that H. pylori presents other components involved in acid resistance.
  
  
  OBJECTIVE
  Here, we present some evidence that the arginine decarboxylase gene (speA) in H. pylori could be involved in an acid adaptation mechanism similar to the one in Enterobacteriaceae, which is dependent on the presence of arginine.
  
  
  METHODS
  Indeed, speA mRNA and protein expression are acutely induced by acid stress.
  
  
  RESULTS
  Moreover, we showed that H. pylori uses arginine in an acid response mechanism required for its growth in acid conditions.
  
  
  CONCLUSIONS
  Altogether, these results provide novel information regarding the H. pylori physiology and acid response mechanism.
authors.affiliation: Faculty of Medicine, Department of Molecular and Cellular Biology, Laboratory of Molecular Microbiology, ICBM, University of Chile, Santiago, Chile; Toxicology and Cancer Biology Research Group, Louvain Drug Research Institute, Université Catholique de Louvain, Bruxelles, Belgium.
authors.forename: Manuel
authors.initials: M
authors.lastname: Valenzuela
authors.forename: Aníbal
authors.initials: A
authors.lastname: Cáceres
authors.forename: Oscar
authors.initials: O
authors.lastname: Almarza
authors.forename: Denisse
authors.initials: D
authors.lastname: Bravo
authors.forename: Sarita
authors.initials: S
authors.lastname: Soto
authors.forename: Oscar
authors.initials: O
authors.lastname: Cerda
authors.forename: Héctor
authors.initials: H
authors.lastname: Toledo
mesh_terms: D000143:Acids / Q000633:toxicity*; D002262:Carboxy-Lyases / Q000235:genetics / Q000378:metabolism*; D004361:Drug Tolerance; D020869:Gene Expression Profiling; D016480:Helicobacter pylori / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D006706:Homeostasis; D006801:Humans; D006863:Hydrogen-Ion Concentration
chemical_list: D000143:Acids; D002262:Carboxy-Lyases; C019722:arginine decarboxylase
keywords: Helicobacter pylori; acidic pH; adiA; agmatine; arginine decarboxylase; speA