Bacteriophage P22 accessory recombination function

Abstract

The accessory recombination function ( arf) gene of bacteriophage P22 is located immediately upstream of the essential recombination function ( erf) gene. Three mutant alleles of arf were constructed and installed in P22 in place of the wild-type allele: an out-of-frame internal deletion, an in-frame internal deletion, and an amber mutation. The deletion mutant phages are partially defective in homologous recombination and plaque formation in wild-type and recA hosts; their defects are more severe in recB and recA recB hosts. The amber mutant phage exhibits the same growth phenotypes in nonsuppressing hosts, but not in an amber-suppressor host. Plasmids that express arf complement the growth defect of arf − phages. These plasmids stimulate erf-mediated recombination; they were also found to cause a small stimulation of recA-recBCD-mediated homologous recombination of phage λ.