Evidence of cell fragility caused by gene kil following lambda induction

Escherichia coli cells carrying lambda cI857 prophage lyse 40 min after lambda thermoinduction; the lysis depends on the lambda genes Q, R, and S. If chloramphenicol (CAP) is added within 20 min after lambda cI857 induction, an early, unproductive lysis occurs. This lysis is independent of the genes int, rex, O, P, Q, and all late genes. Instead, early lysis depends upon the kil gene. The early lysis is under the positive control of lambda gene N and the negative control of gene cro. One or more events specifically connected with lambda induction appear to be necessary for the occurrence of early lysis, since early lysis cannot be observed after lambda infection. Induced lambda kil+ lysogens are more sensitive to osmotic shock than induced lambda kil- lysogens. CAP-induced early lysis can be prevented in a hypertonic medium. These results suggest that induction of lambda causes an osmotic fragility due to a damage of the cell envelope which requires repair; in the absence of protein synthesis the cell envelope is not repaired and cell lysis ensues.