Novel Patterns of Ultraviolet Mutagenesis and Weigle Reactivation in Staphylococcus aureus and Phage o11

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Abstract
The effects of UV irradiation on the survival of S. aureus and its phage .vphi.11 were studied. The recA and uvr mutations affected their survival in a similar way to synonymous mutations in Escherichia coli. Weigle reactivation (W-reactivation) of phage .vphi.11 occurred in wild-type S. aureus and in a uvr mutant but to a lesser extent than has been found for phage .lambda. in E. coli. Reactivation was recA-dependent and was accompanied by UV-induced mutagenesis in a temperature sensitive mutant of phage .vphi.11. Bacterial mutation to streptomycin resistance was induced by UV and was also recA-dependent. In S. aureus, as in E. coli UV was a more effective mutagen in the uvr genetic background. A dose-squared response for UV-induced mutation of wild-type and uvr strains of S. aureus to streptomycin resistance, and of a trp auxotroph to tryptophan independence, was found only with UV doses below 1 J m-2. In relation to the Uvr mechanism of DNA repair, UV mutagenesis in S. aureus may involve repairable and non-repairable lesions. As in E. coli, the uvr genetic background reduced the UV dose required for maximal W-reactivation of UV-irradiated phage. There was no enhancement of W-reactivation by post-irradiation broth incubation of S. aureus. These results are compatible with a non-inducible mechanism for this phenomenon.