Aerobic Metabolism of Streptococcus agalactiae

Streptococcus agalactiae cultures possess an aerobic pathway for glucose oxidation that is strongly inhibited by cyanide. The products of glucose oxidation by aerobically grown cells of S. agalactiae 50 are lactic and acetic acids, acetylmethylcarbinol, and carbon dioxide. Glucose degradation products by aerobically grown cells, as percentage of glucose carbon, were 52 to 61% lactic acid, 20 to 23% acetic acid, 5.5 to 6.5% acetylmethylcarbinol, and 14 to 16% carbon dioxide. There was no evidence for a pentose cycle or a tricarboxylic acid cycle. Crude cell-free extracts of S. agalactiae 50 possessed a strong reduced nicotinamide adenine dinucleotide (NADH(2)) oxidase that is also cyanide-sensitive. Dialysis or ultrafiltration of the crude, cell-free extract resulted in loss of NADH(2) oxidase activity. Oxidase activity was restored to the inactive extract by addition of the ultrafiltrate or by addition of menadione or K(3)Fe(CN)(6). Noncytochrome iron-containing pigments were present in cell-free extracts of S. agalactiae. The possible participation of these pigments in the respiration of S. agalactiae is presently being studied.