A Study of Radiosensitive and Radioresistant Mutants of Escherichia coli strain B

Abstract

SUMMARY Relative differences in radiosensitivity between Escherichia coli strain B and the mutant strains, B/r (more resistant than B) and two types of Bs (more sensitive), are maintained with respect to inactivation by ultraviolet radiation, X-rays and decay of incorporated 32P. The differences cannot be ascribed to variations in number of nuclei or in content of DNA or RNA. The effectiveness of various postirradiation and post-decay treatments in preventing inactivation varies for each strain. With the exception of reactivation by light, strain B/r is less reactivable than B and Bs. The strains do not differ in their rates of mutation to resistance to bacteriophage T1. However, the rates of mutation of the Bs mutants to the first step of furacin- resistance are considerably lower than the rate for the parent strain B. From one of the Bs mutants, new strains were obtained whose properties are mixtures of those of B and B/r.