Altered bacteriophage lambda expression in cell division mutants capR(lon) of Escherichia coli K-12

Summary

Lambda phage containing double amber mutations in the N gene (λc1857N7N53) can replicate and produce progeny phage in capR(lon) bacteria, but not in isogenic capR ⁺ (lon⁺) bacteria, when two additional mutations conferring weak suppression (supE44 and str-109) are present. Since weak suppression was necessary, the capR mutation does not provide a bacterial substitute for the N gene. In an attempt to explain and to relate the phenomenon with the finding that λ⁺ forms clear plaques on capR lawns and lysogenizes capR strains poorly N gene-dependent transcription, translation and functional mRNA decay was measured using a λlac phage in which β-galactosidase (β gal) synthesis is dependent on the N⁺ gene of the phage (λplacW205). No measurable difference in initiation of λ leftward N-dependent transcription or translation was observed in a capR strain compared to an isogenic capR ⁺ strain. A differencewas found in the rate of synthesis of N-dependent β-gal however, between λ-infected capR and capR ⁺ bacteria. λplacW205-infected capR9 strains exhibited a 2 to 4 fold lower rate of β-gal synthesis. This decreased rate of β-gal synthesis was the result of the size heterogeneity of the capR cells when grown in complex medium. That is, complex medium-induced capR filaments synthesized lower amounts of N-dependent β-gal. The results are discussed in relation to the findings in other laboratories.