Inhibition of Coliphage Reproduction after Superinfection of Induced Lysogens

Abstract

Brenner, Don J. (University of Washington, Seattle), and Neal B. Groman . Inhibition of coliphage reproduction after superinfection of induced lysogens. J. Bacteriol. 92: 1727–1734. 1966.—Purified preparations of phages λ and λ112 inhibited lysis, phage reproduction, and endolysin synthesis by ultraviolet-induced strains of K-12 (λ) and K-12 (λ112). Structural and partial functional integrity of phage was required for inhibition, and the role of phage deoxyribonucleic acid (DNA) in inhibition was demonstrated. Both ultraviolet-irradiated and host-modified lysates of λ were inhibitory, suggesting that replication of superinfecting phage DNA was not essential for inhibition. Using various combinations of superinfecting and resident phage, including λ, 434, 434hy, and C -mutant derivatives, we observed that all three C region cistrons played some role in inhibition. Of the three, the C 1 cistron was the most critical. With certain phage combinations, inhibition was observed even though the resident and superinfecting phage differed in immune specificity. Both the medium and the method of superinfection determined whether lysis or lysis inhibition would occur. These and other observations with K-12(λ) thy − indicated that many factors influence the outcome of superinfection. The data are compatible with the view that superinfection inhibition is due to the establishment or re-establishment of phage repressor activity, with the result that replication of both superinfecting and resident phage is blocked.