Lysis defective mutants of bacteriophage lambda: Genetics and physiology of S cistron mutants

Abstract

Five lysis-deficient isolates of the S type, (including sus, def, and one ts mutant), were characterized genetically and physiologically. All the isolates were found to share two distinctive phenotypic properties; susceptibility of host cells to chloroform-induced lysis, and overproduction of phage relative to wild-type or R-mutant yields. Complementation tests demonstrated that the sus and def isolates belong to the S cistron. Two- and three-factor genetic crosses showed that all five markers are closely linked, and located the S cistron between cistrons Q and R. Comparison of the kinetics of production of phage and phage components (serum-blocking material and DNA) by S and R mutants and wild-type phage, showed that overproduction by S mutants is achieved by prolongation of component synthesis and maturation. The failure of R mutants to overproduce even though the host cells do not lyse shows that expression of the S function is responsible for the cessation of phage synthesis at the end of the normal latent period.