Effect of Oxygen on Viability and Substrate Utilization in Chromatium

Chromatium D can be exposed to oxygen for prolonged periods without any loss in motility or viability. Oxygen did not affect the rate of thiosulfate disappearance from the media, the oxidation of the inner sulfur atom of thiosulfate to sulfate, or the conversion of the outer sulfur atom of thiosulfate to intracellular sulfur, but it did inhibit the oxidation of intracellular sulfur to sulfate. Oxygen partially inhibited the uptake of pyruvate from the medium, but had little effect on the uptake of acetate. The distribution of label from pyruvate-2-(14)C into various cell fractions under aerobic conditions differed only slightly from that obtained under anaerobic conditions. Cells utilizing acetate-2-(14)C aerobically converted the majority of the metabolized acetate into a cell fraction with the solubility characteristics of poly-beta-hydroxybutyric acid, whereas under anaerobic conditions the acetate was distributed throughout the other cell fractions. Oxygen completely prevented the synthesis of bacteriochlorophyll.