As earlier reported a temperature-sensitive mutant of Escherichia coli K12 has been isolated which is specifically defective in membrane lipid biosynthesis at 42°. Infection of this mutant with phage T4B at 35° is normal. In contrast, the infection of mutant cultures at 42° is completely abortive. Experiments in which infection was initiated at 35° followed by a shift to 42° at various times during the latent period indicate that sensitivity to temperature shift persists throughout the latent period. It was shown that temperature shift results in a sudden cessation of phage and lysozyme biosynthesis, which is soon followed by a premature lysis of the infected cell. This lysis begins a few minutes after the shift in temperature if the shift is made during the first 70% of the latent period. Experiments using a phage mutant defective in lysozyme biosynthesis indicate that lysozyme is required for the premature lysis caused by temperature shifts late in the latent period. These experiments indicate that the phospholipid biosynthesis which occurs after infection is required for the integrity of the infected cell and hence for successful infection.
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