Properties of a cryptic high-frequency transducing phage in Staphylococcus aureus

Abstract

A high-frequency transducing element for erythromycin resistance in Staphylococcus aureus has been found. This element, P11 de, is apparently the result of a recombinational event between a temperate phage, P11, and a penicillinase plasmid, γ; it lacks substantial sections both of the plasmid and of the bacteriophage. The phage moiety is cryptic, conferring neither lysogeny nor superinfection immunity upon host cells carrying it; helper phage is required for the production of transducing particles but not for the transduction process. Demonstrable phage-related properties include reactivation of ultraviolet-inactivated homologous phage and rescue of temperature-sensitive phage mutants. The plasmic moiety includes an erythromycin resistance marker, and the mc region, which is responsible for plasmid compatibility, is involved in a specific host-plasmid interaction and is required for plasmid replication; all the other known plasmid markers are missing. The autonomous replication of P11 de as well as its intracellular behavior vis-à-vis prophages and other plasmids appear to be governed by its mc determinant. In these respects P11 de is similar to the parental γ plasmid. This plasmid control, however, is superseded by active P11, which induces P11 de to multiply extensively. P11 de can recombine with wild-type plasmids; the resulting recombinants are not transduced at high frequency, nor do they reactivate UV inactivated phage particles. Based on these findings, a possible genetic structure for P11 de is presented and compared with maps of naturally occurring plasmids.