NATURE OF THE DETERMINANT CONTROLLING PENICILLINASE PRODUCTION INSTAPHYLOCOCCUS AUREUS

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Abstract
From three penicillinase-producing strains of Staphylococcus aureus 38 penicillin-sensitive mutants were isolated. With phages 80 and 53 of the International Typing Series, each of these mutants was a competent recipient of the penicillinase marker from the parent strains. Although numerous reciprocal transductions were performed between penicillin-sensitive mutants, no penicillinase-producing recombinants were observed. Reversion of the penicillinase-negative mutants to capacity to produce penicillinase was never observed. When tested for 50 distinctive physiological characteristics, the mutants generally were similar to the parent strains except for resistance to penicillin. One penicillin-sensitive mutant failed to produce detectable amounts of five exoenzymes. By treating resistant strains with acridine orange, it was possible to isolate sensitive strains at a frequency that was 60 times greater than the spontaneous mutation rate. Thus, the determinant controlling the capacity of strains of S. aureus to produce penicillinase appears to be a cytoplasmic element.