In 1957, Yabe reported that the combined administration of glutamate and glucose markedly accelerated the respiration of Micrococcus pyogenes var. aureus (Terashima) over the sum of those in each of the two substrates, and that this phenomenon was due to the important role of glutamate as a sole sparker or entering site of the citric acid cycle of M. pyogenes var. aureus (Terashima). In the present experiments, the authors investigated this phenomenon in regard to pH. In the presence of glutamate and glucose, oxygen consumption or carbon dioxide evolution was nearly the same at all pHs tested, whereas ammonia formation was the best at pH 6.2, which was the optimum for glutamate oxidation by M. pyogenes var. aureus (Terashima); this result seems to sustain the conclusion given by Yabe. For all of glutamate, aspartate and alanine, the oxidation optimum pHs were lower in M. pyogenes var. aureus (Terashima) than in pyogenes var. albus and citreus. From thsee results, it is easily inferred that the cytoplasmic membrane of M. pyogenes var. aureus (Terashima) is a pretty peculiar one compared with those of the other two micrococci, and that these peculiar physiological properties of the cytoplasmic membrane have something to do with the previously reported peculiar aspect of the citric acid cycle of M. pyogenes var. aureus (Terashima).