The isolation and some properties of radiation-sensitive mutants of Micrococcus radiodurans

SUMMARY: Treatment of the radiation-resistant bacterium Micrococcus radiodurans with ultraviolet (u.v.) radiation and N-methyl-N'-nitro-N-nitrosoguanidine resulted in the isolation of two mutants highly sensitive to u.v. radiation. They were also sensitive to ionizing radiation and to the action of N-methyl-N'-nitro-N-nitrosoguanidime. The concentrations of sulphydryl groups in bacteria of the wild type and the mutants were not significantly different. Although the mutants were more sensitive to mitomycin C than the wild type the resistance of the latter was low. It is suggested that the DNA repair mechanism in the wild type operates very efficiently for the removal of single strand damage but not for that which involves cross-linking.