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

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Abstract
Differences in radiosensitivity between Escherichia coli strain B, the mutant strain B/r (more resistant than B), and two strains Bs (more sensitive), are observed with respect to inactivation by ultraviolet radiation, X-rays and decay of incorporated p32. The differences cannot be ascribed to variations in number of nuclei or in content of deoxyribonucleic acid or ribonucleic acid. The effectiveness of various post-irradiation 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.