SURFACE LOCALIZATION OF HELICOBACTER-PYLORI UREASE AND A HEAT-SHOCK PROTEIN HOMOLOG REQUIRES BACTERIAL AUTOLYSIS

Helicobacter pylori is a gram-negative bacterium which causes chronic gastritis and is associated with peptic ulcer disease, gastric carcino ma, and gastric lymphoma. The bacterium is characterized by potent ure ase activity, thought to be located on the outer membrane, which is es sential for survival at low pH. The purpose of the present study was t o investigate mechanisms whereby urease and HspB, a GroEL homolog, bec ome surface associated in vitro. Urease, HspB, and catalase were locat ed almost exclusively within the cytoplasm in fresh log-phase cultures assessed by cryo-immunoelectron microscopy. In contrast, significant amounts of surface-associated antigen were observed in older or subcul tured preparations concomitantly,vith the appearance of significant am ounts of extracellular antigen, amorphous debris, and membrane fragmen ts, By use of a variety of biochemical methods, a significant fraction of urease and HspB was associated with the outer membrane in subcultu red preparations of H. pylori. Taken together, these results strongly suggest that H. pylori cells undergo spontaneous autolysis during cult ure and that urease and HspB become surface associated only concomitan t with bacterial autolysis. By comparing enzyme sensitivity to flurofa mide (a potent, poorly diffusible urease inhibitor) in whole cells wit h that in deliberately lysed cells, we show that both extracellular an d intracellular urease molecules are active enzymatically, Autolysis o f H. pylori is an important phenomenon to recognize since it likely ex erts significant effects on the behavior of H. pylori, Furthermore, th e surface properties of H. pylori must be unique in promoting adsorpti on of cytoplasmic proteins.