Role of the bacterial and phage recombination systems and of DNA replication in genetic recombination of UV-irradiated phage lambda

Summary In this paper are studied in E. coli K12 the influence of the bacterial Rec and phage Red recombination systems on the rescue of the O ⁺ gene from the prophage by a superinfecting O ^- phage, UV irradiated or not. In the absence of UV irradiation the Red system produces more recombinants that does the Rec system, and its action requires DNA replication. The presence of UV lesions in the DNA facilitates the action of the Rec system, which is more efficient in this instance than the Red system and can act in the absence of DNA replication. In all cases, there is a cooperation between the two generalized recombination systems.