The bactericidal and morphological effects of peroxynitrite on Helicobacter pylori

Peroxynitrite (ONOO-) is correlated with the pathogenesis of Helicobacter pylori-induced peptic ulcer diseases. We aimed to investigate the time- and concentration-dependent bactericidal and morphological effects of ONOO- on H. pylori. Authentic ONOO- was synthesized as quenched-flow method. A stock culture of H. pylori NCTC 11637 was exposed to different concentrations of ONOO- (0.1-40 micromol/L) or decomposed ONOO- or fresh medium. Samples were taken at 0, 15, 30, 60, and 120 minutes, for the evaluation of viable bacteria and bacterial morphology with gram strain and transmission electron microscopy. Decomposed ONOO- showed no bactericidal activity against H. pylori. ONOO- application caused a decrease in the number of viable bacteria within the first 15 minutes. The significant conversion of H. pylori from spiral form to coccoid form was determined with 10 micromol/L of ONOO-, and higher concentrations caused lysis of the cells. Separation of cell wall, bleb formation, vacuolization, decrease of secretory granules, and lysis of bacteria were the morphological effects of ONOO- on H. pylori. Because the morphology of the bacteria is one of the important factors in virulence; peroxynitrite-related morphological effects might have an impact in the progress of the H. pylori-induced peptic ulcer diseases.