title: Integration and induction of phage P22 in a recombination-deficient mutant of Salmonella typhimurium.
abstract: Phage P22 can integrate as prophage into a recombination-deficient (Rec(-)) strain of Salmonella typhimurium. At 37 C, the integration efficiency is only 10% that in Rec(+) infection, but at 25 C the efficiencies in Rec(-) and Rec(+) hosts are similar. Rec(-) lysogens cannot be induced by ultraviolet irradiation or by treatments with the chemical inducing agents streptonigrin or mitomycin C. Heat induction of Rec(-) cells lysogenic for a temperature-sensitive c(2) mutant (ts c(2)) is normal, showing that the Rec(-) cell has the machinery necessary for prophage excision. Ultraviolet irradiation of Rec(-) (ts c(2)) lysogens prior to heat induction does not prevent the formation of infective centers after temperature shift. Thus, the noninducibility of Rec(-) lysogens is not due to destruction of the prophage as a result of ultraviolet irradiation. Deoxyribonucleic acid-ribonucleic acid (RNA) hybridization experiments demonstrate that no increase in phage-specific RNA synthesis occurs after ultraviolet irradiation of a Rec(-) (c(+)) lysogen. The Rec(-) mutant appears to lack part of the mechanism required to destroy the phage repressor and allow the initiation of early phage functions such as messenger RNA synthesis. A similar conclusion was reached previously for an Escherichia coli Rec(-) strain.
mesh_terms: D006358:Hot Temperature; D008242:Lysogeny; D008937:Mitomycins / Q000494:pharmacology; D009154:Mutation; D011995:Recombination, Genetic; D012483:Salmonella Phages / Q000528:radiation effects; D012486:Salmonella typhimurium; D013308:Streptonigrin / Q000494:pharmacology; D014466:Ultraviolet Rays
chemical_list: D008937:Mitomycins; D013308:Streptonigrin