Electron transport chain in aerobically cultivated Zymomonas mobilis

Abstract

Respiratory chain composition and energy coupling in cytoplasmic membrane of Zymomonas mobilis was shown to depend on culture aeration. Aerobically grown cells contained mainly the non-energy-generating NADH dehydrogenase with k M for NADH 58 mM. In anaerobically cultivated bacteria, the energy-coupling NADH dehydrogenase complex with k m for NADH 7 mM predominated. In aerobically cultivated Z. mobilis, CoQ content and absorption peaks of cytochromes at 554–556 nm and 525–528 nm were significantly increased. Energy-coupling site I, linked to the NADH:CoQ oxidoreductase complex, could be eliminated under sulfate-déficient cultivation conditions. For anaerobically grown cells this resulted in loss of oxidative phosphorylation activity, while in aerobically grown cells energy coupling was not affected. These findings indicate a shift of energy coupling from site I to the cytochrome region of the respiratory chain in Z. mobilis under transition from anaerobic to aerobic growth conditions.