Role of Erf recombinase in P22-mediated plasmid transduction.

In the absence of host RecA function, plasmid transduction by bacteriophage P22 can be mediated by Erf recombinase. Erf is not carried on the infecting particle but synthesized upon infection. In the recipient cell, Erf can promote both generalized plasmid transduction (which requires the circularization of plasmids transduced as linear multimers) and specialized plasmid transduction (which requires the release of plasmid DNA from linear plasmid-phage cointegrates). Both processes of Erf-mediated plasmid transduction require host RecBCD function. In contrast, RecBCD is not required for Erf-mediated circularization of P22 DNA.