Micrococci Demonstrate a Phosphatase Activity Which Is Repressed by Phosphates and Which Can Be Differentiated from That of Staphylococci

Abstract

The phosphatase activities of 114 micrococcal strains belonging to seven 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 strains (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 phosphatase could not be evaluated on solid media since none of the strains grew satisfactorily on plates at pH 5. The phosphatase activities of seven (one or two for each species, which included phosphatase-negative strains) of the strains whose colonies proved phosphatase negative at pH 8 and of 18 (two or three strains per species) of those with phosphatase-positive colonies were evaluated at pH 5 and 8.5 in toluene-treated cells which had been grown in liquid media at pH 7 containing or not containing phosphates. All strains demonstrated distinct phosphatase activity at both pHs when grown in media not containing phosphates. In 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 micrococci of the various species (three to eight strains per species) was also compared with that of staphylococci of different species (5 to 10 strains per species) by the methyl green-phenolphthalein diphosphate method, the sensitivity of which can be varied by using different enzyme substrates. By using phenolphthalein diphosphate as an enzyme substrate, it was found that virtually all the different species of staphylococci yielded a positive reaction on plates not containing phosphates while almost all micrococci proved phosphatase negative with the methyl green-phenolphthalein diphosphate method. This indicates that the phosphatase activity of micrococci can easily be differentiated from that of staphylococci.Of the metabolic properties generally exploited for defining and characterizing the different bacterial species, such as enzyme activities and sugar fermentation, only a few have so far been identified in micrococci. This leaves us with relatively few tests that, particularly in some species (see reference 17), can be used for characterizing the various strains of the group. This is rather unfortunate since it makes micrococcal species definition and identification difficult, particularly with the standard type of assays generally performed in routine clinical microbiology. However, it is likely that further studies may lead to identification of additional metabolic properties that may prove useful for characterization of this bacterial group.Phosphatase activity is a property often evaluated as a test for species definition and identification (3,10,12,15,48). However, it has not yet been extensively analyzed for micrococci. From ...

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“…Other gram positive cocci that can be found in food or clinical samples are micrococci, streptococci and enterococci. Micrococci do not produce phosphatase when grown in presence of 0.3 % Pi (Satta, D'andrea, Grazi, Soro, & Varaldo, 1993) while enterococci and streptococci may produce phosphatase but are coagulase negative. Staphylococci and streptococci can be differentiated by Catalase test.…”