title: A novel mechanism of autolysis in Helicobacter pylori: possible involvement of peptidergic substances.
abstract: BACKGROUND
  Helicobacter pylori survival in a hostile acidic environment is known to be caused by its production of urease, which is not released by known secretion pathways. It has been proposed that H. pylori cells undergo spontaneous autolysis during cultivation and that urease becomes surface-associated only concomitant with bacterial autolysis. The aim of this study was to elucidate mechanisms by which H. pylori cells undergo autolysis during cultivation.
  
  
  METHODS
  Autolysis of H. pylori KZ109 cells was estimated by measuring the turbidity of the culture, by detection of cytoplasmic protein release into the culture supernatant and by scanning electron microscopic observation of H. pylori cells during cultivation. An autolysis-inducing factor (AIF) was partially purified from the culture supernatant by a partition method using ethyl acetate.
  
  
  RESULTS
  Bacterial turbidity of KZ109 cells was drastically decreased after late-log phase accompanying release of urease and HspB into the extracellular space. Concomitantly, cell lytic activity was detected in the culture supernatant. Scanning electron microscopic observation suggested that partially purified AIF induced cell lysis. It was also shown that the AIF is different from other autolytic enzymes or substances so far reported.
  
  
  CONCLUSIONS
  This study demonstrated the presence of the peptidergic autolytic substances in the culture supernatant of H. pylori KZ109 cells. The results of this study should be useful for further studies aimed at elucidation of the strategy of survival of H. pylori in the gastric environment and elucidation of the mechanisms of pathogenesis induced by H. pylori.
authors.affiliation: Laboratory of Biomolecular Function, School of Veterinary Medicine and Animal Sciences, Kitasato University, Towada, Aomori 034-8628, Japan.
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Fujita
authors.forename: Kosaku
authors.initials: K
authors.lastname: Yamaguchi
authors.forename: Taichi
authors.initials: T
authors.lastname: Kamegaya
authors.forename: Hiroko
authors.initials: H
authors.lastname: Sato
authors.forename: Kayoko
authors.initials: K
authors.lastname: Semura
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Mutoh
authors.forename: Takashige
authors.initials: T
authors.lastname: Kashimoto
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Ohori
authors.forename: Takao
authors.initials: T
authors.lastname: Mukai
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism* / Q000494:pharmacology; D001433:Bacteriolysis / Q000187:drug effects / Q000502:physiology*; D016123:Campylobacter jejuni / Q000187:drug effects / Q000502:physiology; D017077:Culture Media, Conditioned / Q000737:chemistry; D003593:Cytoplasm / Q000378:metabolism; D016480:Helicobacter pylori / Q000187:drug effects / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure; D006801:Humans; D008855:Microscopy, Electron, Scanning; D010455:Peptides / Q000378:metabolism* / Q000494:pharmacology; D013104:Spheroplasts / Q000502:physiology / Q000648:ultrastructure; D014510:Urease / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D017077:Culture Media, Conditioned; D010455:Peptides; D014510:Urease