MICROCOCCI DEMONSTRATE A PHOSPHATASE-ACTIVITY WHICH IS REPRESSED BY PHOSPHATES AND WHICH CAN BE DIFFERENTIATED FROM THAT OF STAPHYLOCOCCI

The phosphatase activities of 114 micrococcal strains belonging to sev en different species and of an additional 150 unspeciated micrococcal strains were evaluated on solid media at various pHs containing or not containing phosphates. In the presence of phosphates, only nine strai ns (five unspeciated strains, one Micrococcus luteus strain, and three Micrococcus varians strains) yielded a positive reaction on plates at pH 8. In media (at pH 8) deprived of phosphates, in contrast, all but 15 strains demonstrated clear-cut phosphatase activity. Acid phosphat ase could not be evaluated on solid media since none of the strains gr ew satisfactorily on plates at pH 5. The phosphatase activities of sev en (one or two for each species, which included phosphatase-negative s trains) of the strains whose colonies proved phosphatase negative at p H 8 and of 18 (two or three strains per species) of those with phospha tase-positive colonies were evaluated at pH 5 and 8.5 in toluene-treat ed cells which had been grown in liquid media at pH 7 containing or no t containing phosphates. All strains demonstrated distinct phosphatase activity at both pHs when grown in media not containing phosphates. I n contrast, when strains were grown in the presence of such substances , virtually no activity was observed at pH 8.5, and, generally, a much reduced activity was observed at pH 5. The phosphatase activity of mi crococci of the various species (three to eight strains per species) w as also compared with that of staphylococci of different species (5 to 10 strains per species) by the methyl green-phenolphthalein diphospha te method, the sensitivity of which can be varied by using different e nzyme substrates. By using phenolphthalein diphosphate as an enzyme su bstrate, it was found that virtually all the different species of stap hylococci yielded a positive reaction on plates not containing phospha tes while almost all micrococci proved phosphatase negative with the m ethyl green-phenolphthalein diphosphate method. This indicates that th e phosphatase activity of micrococci can easily be differentiated from that of staphylococci.