A novel mechanism of autolysis in Helicobacter pylori: possible involvement of peptidergic substances.
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.
Fujita
Yukihiro
Y
Laboratory of Biomolecular Function, School of Veterinary Medicine and Animal Sciences, Kitasato University, Towada, Aomori 034-8628, Japan.
Yamaguchi
Kosaku
K
Kamegaya
Taichi
T
Sato
Hiroko
H
Semura
Kayoko
K
Mutoh
Kenichiro
K
Kashimoto
Takashige
T
Ohori
Hitoshi
H
Mukai
Takao
T
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
D001426:Bacterial Proteins; D017077:Culture Media, Conditioned; D010455:Peptides; D014510:Urease