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Abstract
Selenomonas ruminantium WPL 151/1 was grown in continuous culture anaerobically and at different gas phase partial pressures of oxygen (pO2). Low pO2 values led to substantial increases in whole-cell potential oxygen consumption rates and in NADH oxidase and superoxide dismutase activities in cell extracts. At the same time, concentrations of certain cytochrome pigments fell whilst lactate and acetate concentrations increased in the culture. As the pO2 was increased, growth yield became progressively lower, culture Eh became more positive and respiratory activity and NADH oxidase and superoxide dismutase activities fell. At these pO2 values cytochrome concentrations increased and fermentation products became more oxidized. Above a gas phase pO2 of 36·7 mmHg the culture began to wash out of the vessel. It is concluded that NADH oxidase and superoxide dismutase play an important part in protecting S. ruminantium against oxygen toxicity.
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