TEMPERATURE AND THE REPRODUCTION OF LAMBDA-PHAGE MUTANTS

Abstract

Groman, Neal B. (University of Washington, Seattle). Temperature and the reproduction of two lambda-phage mutants. J. Bacteriol. 84: 438–445. 1962.—A comparative study of phage λ, and mutants λ tem and λ 11 2 , was made, with particular emphasis on the effect of elevated temperature (44 C) on phage reproduction. Phage λ tem was selected at 44 C and λ 11 2 was isolated from the late-lysing fraction of bacteria at 37 C. All three phages are similar in their host range, immunity pattern, and in the rate of inactivation of free phage by anti-λ antibody and heat. Differences were observed in their plaque size and in their relative plating efficiency at 37 and 44 C. One-step growth curve studies showed that phages λ and λ tem are similar in the time intracellular phage appears and in their rate of maturation at 37 C. These time and rate parameters were unchanged at 44 C. Both λ and λ tem exhibited a reduced latent period at 44 C. However, the latent period of λ tem was longer than that of λ at both 37 and 44 C, and its relative 44 C/37 C yield was about 40% while that of lambda is about 3%. Phage λ tem may be characterized as a λ mutant with an altered latent period. Phage λ 11 2 was similar to λ and λ tem at 37 C, but at 44 C behaved quite differently. The time of appearance of intracellular phage was delayed, compared to 37 C, and the rate of maturation was slower. Phage production at 44 C was about 16% that at 37 C. On further investigation, it was observed that induced Escherichia coli K-12 (λ 11 2 ) failed to lyse at 44 C, although it did lyse at 37 C. Lysis inhibition was imposed almost immediately by transferring cells from 37 C to 44 C at any time during the reproductive cycle, including the lytic phase. The behavior of λ 11 2 at 44 C disposed of the possibility that the lytic step was the only step in the phage cycle sensitive to variations in temperature. However, it appeared that the lytic step was a consistant target for its action.