FACTORS MODIFYING INDUCED FORMATION OF PENICILLINASE IN STAPHYLOCOCCUS AUREUS

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Abstract
Induced formation of penicillinase by Staphylococcus aureus, which was proportional to the number of cells at low cell concentrations, failed to occur, under certain circumstances, in the presence of an excessive number of organisms. The bactericidal effect of high inducing concentrations of penicillin placed a lower limit on the concentration of organisms which remained inductible. A chemically defined medium could be substituted for broth media in the induction reaction. Two broth media, which exhibited only a slight difference in their abilities to support induced enzyme formation in the presence of glucose, were significantly different in the absence of glucose. When the same strain of S. aureus was grown in the 2 broth media, the progeny displayed a striking dissimilarity in their glucose requirement for induction in a defined medium. Cultures aged either by storage or by aeration showed decreased inducibility. The rate of formation of penicillinase was optimal in growing cultures derived from physiologically young cells. The inducing concentration of penicillin G required to attain half the maximum amount of enzyme was 100 units per ml. For a specific size of inoculum, this concentration was independent of the induction medium, whether complex or defined.