Respiratory Development in Saccharomyces cerevisiae Grown at Controlled Oxygen Tension

Abstract

Saccharomyces cerevisiae was grown in batch culture over a wide range of oxygen concentrations, varying from the anaerobic condition to a maximal dissolved oxygen concentration of 3.5 μM. The development of cells was assayed by measuring amounts of the aerobic cytochromes aa 3 , b, c , and c 1 , the cellular content of unsaturated fatty acids and ergosterol, and the activity of respiratory enzyme complexes. The half-maximal levels of membrane-bound cytochromes aa 3 , b , and c 1 , were reached in cells grown in O 2 concentrations around 0.1 μM; this was similar to the oxygen concentration required for half-maximal levels of unsaturated fatty acid and sterol. However, the synthesis of ubiquinone and cytochrome c and the increase in fumarase activity were essentially linear functions of the dissolved oxygen concentration up to 3.5 μM oxygen. The synthesis of the succinate dehydrogenase, succinate cytochrome c reductase, and cytochrome c oxidase complexes showed different responses to changes in O 2 concentration in the growth medium. Cyanide-insensitive respiration and P 450 cytochrome content were maximal at 0.25 μM oxygen and declined in both more anaerobic and aerobic conditions. Cytochrome c peroxidase and catalase activities in cell-free homogenates were high in all but the most strictly anaerobic cells.