HELICOBACTER-PYLORI GENERATES SUPEROXIDE RADICALS AND MODULATES NITRIC-OXIDE METABOLISM

During studies of the bactericidal action of nitric oxide (NO), we fou nd that it reversibly inhibited the respiration of Escherichia coli an d irreversibly inhibited the respiration of Helicobacter pylori. Perox ynitrite, a reaction product of NO and superoxide, irreversibly inhibi ted the respiration of both H. pylori and E. coli. H. pylori, but not E. coli, generated substantial amounts of superoxide radicals. These r esults suggest that NO directly inhibits the respiration of E. coli wh ereas it rapidly reacts with endogenously generated superoxide radical s in H. pylori. The resulting peroxynitrite inactivates the respiratio n of H. pylori.