Bacterial Nutritional Approach to Mechanisms of Oxygen Toxicity

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Abstract
Inhibition by oxygen of growth of the bacterium Achromobacter P6 was released by amino-acid supplements. The reversal of oxygen-induced growth inhibition was not due to the presence of reducing substances in the growth medium. Oxygen primarily exerts a bacteriostatic effect. The oxygen inhibition of growth occurred over a wide pH range. Oxygen inhibition of growth was observed when 1-amino-2-propanol, acetate, lactate, citrate, or glucose was used as the sole source of carbon and energy. No inhibition of growth was obtained when succinate, fumarate, malate, or glutamate was used as the source of carbon and energy. Oxygen markedly depressed the respiration of P6 when l-amino-2-propanol was the substrate. There was no depression of respiration under oxygen with succinate as substrate. P6 grown in the presence of high oxygen tensions had a higher rate of respiration under oxygen than similar air-grown cells. Chloram-phenicol did not affect the rate of oxygen consumption or cause a further depression of the respiratory rate in the presence of oxygen. It is suggested that microbes may serve as a model system for studying the cellular and subcellular mechanisms of oxygen toxicity.