Endogenous respiration of Staphylococcus aureus.

Ramsey, H. H. (Stanford University, Palo Alto, Calif.). Endogenous respiration of Staphylococcus aureus. J. Bacteriol. 83:507-514. 1962.-The endogenous respiration of Staphylococcus aureus is dependent upon the medium used to grow the cell suspension. Within wide ranges, the concentration of glucose in the medium has no effect upon subsequent endogenous respiration of the cells, but the concentration of amino acids in the medium, within certain limits, has a very marked effect. The total carbohydrate content of the cells does not decrease during endogenous respiration. As endogenous respiration proceeds, ammonia appears in the supernatant, and the concentration of glutamic acid in the free amino acid pool decreases. Organisms grown in the presence of labeled glutamic acid liberate labeled CO(2) when allowed to respire without added substrate. The principal source of this CO(2) is the free glutamate in the metabolic pool; its liberation is not suppressed by exogenous glucose or glutamate. With totally labeled cells, the free pool undergoes a rapid, but not total, depletion and remains at a low level for a long time. Activity of the protein fraction declines with time and shows the largest net decrease of all fractions. Exogenous glucose does not inhibit the release of labeled CO(2) by totally labeled cells. Other amino acids in the free pool which can serve as endogenous substrates are aspartic acid and, to much lesser extents, glycine and alanine. The results indicate that both free amino acids and cellular protein may serve as endogenous substrates of S. aureus.