Repression of λ-Associated Enzyme Synthesis After λ vir Superinfection of Lysogenic Hosts

Abstract

Lisio, Arnold L. (National Institutes of Health, Bethesda, Md.), and Arthur Weissbach . Repression of λ-associated enzyme synthesis after λ vir superinfection of lysogenic hosts. J. Bacteriol. 90: 661–666. 1965.—Phage λ vir is a multiple mutant of λ which is capable of overcoming the immunity of a host lysogenic for λ, and initiating normal vegetative replication of the superinfecting phage genome. Superinfection of Escherichia coli K-112 (λ 22 ) with λ vir results in a normal phage yield, lysis time, and H 3 -thymine incorporation compared with infection of the sensitive host, K-112 (S). However, the production of the λ phage-specific early protein, λ-exonuclease, after superinfection of E. coli K-112 (λ 22 ) with λ vir is only 25 to 50% of that obtained from corresponding infection of a nonlysogenic host, E. coli K-112 (S). This repression of λ-exonuclease synthesis is dependent on the C 1 cistron of the prophage and is overcome if the lysogenic host cells are induced prior to superinfection. The data are interpreted as evidence for partial repression of λ vir by the host immunity.