Kinetics and mechanisms of extracellular protein release by Helicobacter pylori

To investigate the kinetics and mechanisms of extracellular protein release by Helicobacter pylori, we analyzed the entry of metabolically radiolabele d bacterial proteins into broth culture supernatant. At early time points, vacuolating cytotoxin (VacA) constituted a major extracellular protein, Sub sequently, culture supernatants accumulated many proteins that were compone nts of intact bacterial cells. This nonselective release of proteins was as sociated with a decreasing turbidity of cultures and loss of bacterial viab ility, indicative of an autolytic process. The rates of VacA secretion and autolysis were each influenced by medium composition, and therefore these m ay be regulated phenomena. Extracellular release of proteins by H. pylori m ay be an important adaptation that facilitates the persistence of H, pylori in the human gastric mucus layer, Moreover, entry of proinflammatory prote ins into the gastric mucosa may contribute to the induction of a mucosal in flammatory response.