Mutations in Prophage φ11 That Impair the Transducibility of Their Staphylococcus aureus Lysogens for Methicillin Resistance

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Abstract
Methicillin resistance (mec) is not transduced into Staphylococcus aureus 8325-4, but is transduced into this host after it has been lysogenized with phage φ11 and has acquired the penicillinase plasmid pI524 by a separate transduction (Cohen and Sweeney, 1970, 1973). Strain 8325-4 is competent for transformation of typical plasmid or chromosomal markers and for mec only if it is lysogenic for φ11 or a related prophage (Sjöström et al., 1974, 1975). A mutant strain of φ11 that was temperature sensitive (Ts) for vegetative multiplication did not mediate competence for transformation of its 8325-4 lysogen if the lysogen had been grown at a nonpermissive temperature (Sjöström and Philipson, 1974). We isolated four Ts mutants of φ11 that did not mediate transducibility of their 8325-4(pI524) lysogens for mec after growth at nonpermissive temperatures (40 to 42°C). Transduction of typical plasmid or chromosomal markers was not affected. These φ11-Ts mutants mediated normal competence of their lysogens for transformation of a tetracycline resistance plasmid. Similarly, φ11-Ts mutants that rendered their lysogens temperature sensitive for transformation did not depress the frequency of transduction of mec. These two types of φ11-Ts mutants fell into two different genetic complementation groups that differed in the physiology of deoxyribonucleic acid synthesis and in the time of expression of the mutations during a single-burst growth cycle at a nonpermissive temperature. A virulent mutant of φ11, which plaqued with 100% efficiency on 8325(φ11), also failed to condition strain 8325-4 for transducibility of mec but retained the ability to confer competence for transformation of a tetracycline resistance plasmid. Different genetic loci and physiological functions are involved in φ11 mutations that affect transducibility of mec and those that affect competence for transformation of markers generally in S. aureus 8325-4.