OXIDATIVE-PHOSPHORYLATION IN ZYMOMONAS-MOBILIS

The obligately fermentative aerotolerant bacterium Zymomonas mobilis w as shown to possess oxidative phosphorylation activity. Increased intr acellular ATP levels were observed in aerated starved cell suspension in the presence of ethanol or acetaldehyde. Ethanol-consuming Z. mobil is generated a transmembrane pH gradient. ATP synthesis in starved Z. mobilis cells could be induced by external medium acidification of 3.5 -4.0 pH units. Membrane vesicles of Z. mobilis coupled ATP synthesis t o NADH oxidation. ATP synthesis was sensitive to the protonophoric unc oupler CCCP both in starved cells and in membrane vesicles. The H+-ATP ase inhibitor DCCD was shown to inhibit the NADH-coupled ATP synthesis in membrane vesicles. The physiological role of oxidative phosphoryla tion in this obligately fermentative bacterium is discussed.