Lambda phage mutants insensitive to temperature-sensitive repressor

Summary

The isolation of λ recombinant carrying virC mutation from newly isolated λ virulent carrying virL virC virR, (Horiuchi et al., 1969) was succeeded and the genetic character of virC mutation producing clear plaque was studied.

λ virL virC shows weak-virulent character and produces clear plaque on λCIts lysogen but not on wild type λ lysogen. λ virC shows avirulent character and no plaque is produced on these lysogen. The virC mutation is located very closely to and on the left side of the virR region (Fig. 1) which is presumed to be the operator of the right-side operon including O and P cistrons. The genetic characters of virL, virR and virC, were compared with v ₁, v ₂, v ₃ mutations of classical λ vir (Jacob and Wollman, 1954) and c ₁₇ mutation of another type of λ virulent (Da Silva and Jacob, 1968). The results indicate that virL, virC or virR mutation is similar to v ₂, v ₁ or v ₃ mutation, respectively, and an effect of virC mutation on producing virulent character was somewhat similar to that of c ₁₇ mutation and was stronger than that of virR mutation. The length of virR regions was suggested to be smaller than one tenth of that of the CI cistron.