KINETICS OF SUBSTRATE OXIDATION BY WHOLE CELLS AND CELL-MEMBRANES OF HELICOBACTER-PYLORI

Oxygen uptake by Helicobacter pylori cells and membranes was determine d. Cells from stirred broth cultures or agar plates, suspended in buff er, possessed a variable and apparently endogenous respiration which c ould be sustained for several hours. In contrast, oxygen consumption b y cells from statically incubated broth cultures, in the absence of ad ded substrate, was transient or undetectable. These latter cells, howe ver, oxidised ethanol, fumarate, glucose, D-lactate, pyruvate and succ inate, though glucose-oxidising ability declined rapidly. The K(m)s fo r D-lactate, pyruvate and succinate metabolism were low (less than or equal to 20 mu M) and oxygen uptake was approximately 1.5, 2 and 2 mol per mol substrate respectively, indicating metabolism beyond acetate plus CO2 and implying the presence of tricarboxylic acid cycle activit y. Cell membranes oxidised fumarate, D-lactate, NADH, NADPH and succin ate. NADPH oxidation was six times more rapid than that of NADH. Rates of oxygen uptake by cells suspended in buffer with metabolisable subs trate were < 20% of those for cells suspended in a brain heart infusio n medium. Uninoculated medium consumed significant quantities of oxyge n.