C. F. Niven

A study of the methylene blue and oxygen inhibition of pyruvate oxidation by Micrococcus pyogenes var. aureus

Abstract The oxidation of pyruvate by resting-cell suspensions of a coagulasepositive, enterotoxin-producing strain of Staphylococcus aureus has been studied. With moderate substrate levels (10–20 μM per Warburg cup) pyruvate was oxidized almost exclusively to acetate, carbon dioxide, and water. The respiratory quotient of this oxidation varied from 1.4 to 1.9 depending on the cell preparation used. The results indicate that some of the substrate was oxidized beyond the acetate level (R.Q., 2.0). Methylene blue or oxygen exerted an inhibitory effect upon pyruvate oxidation, and, under certain conditions, thiamine and magnesium overcame this inhibition. Evidence is presented to support the hypothesis that this organism possesses two separate systems for pyruvate oxidation. Washed-cell suspensions oxidize pyruvate predominantly by a system that is sensitive to methylene blue and oxygen. When this system is inhibited the competing system becomes dominant. However, the washed cells are deficient in thiamine and magnesium for optimum functioning of this latter system. A by-product of this second system is acetoin, indicating that there is an intermediate compound that may be either oxidized to acetate or condensed to form acetoin. If the washed cells are provided with a high substrate level or are supplemented with additional thiamine and magnesium, some of the pyruvate is metabolized by the second pathway even in the absence of an inhibitor for the first system.

COMMENTS ON THE SPECIES STAPHYLOCOCCUS EPIDERMCDIS (WINSLOW AND WINSLOW) EVANS ANDl STAPHYLOCOCCUS SAPROPHY TICUS FAIRBROTHER

ABSTRACT The nomenclature and characterization of Staphylococcus epidermidis (Winslow and Winslow 1908) Evans, 1916 and Staphylococcus saprophyticus Fairbrother, 1940 are reviewed. It is apparent that these names have been applied to one and the same species and are therefore subjective synonyms. On the basis of priority, Staphylococcus epidermidis is the correct name of this species.