Radiosensitivity in Escherichia coli

SUMMARY: A radiosensitive mutant of Escherichia coli strain K12, W3747 was found to be similar to E. coli strains b and s with respect to survival following ultraviolet irradiation, plating-medium recovery, ability to ‘reactivate’ irradiated T1 phage, and in its cross-resistance pattern with radiomimetic chemicals. In all these respects the radiosensitive E. coli strain k12, ab1186, isolated by Howard-Flanders, was found to resemble the Hill radiation hypersensitive strain Bs-1, and, except in the ability to reactivate irradiated T1 phage, strain B s-2. Strains W3747s and ab1886 acquired sensitivity to radiomimetic chemicals concomitantly with radiation sensitivity. Strains Bs-1 and Bs-2 on becoming hypersensitive to radiation did not become correspondingly hypersensitive to radiomimetic chemicals. In fact, they acquired a small degree of resistance to these chemicals, relative to strain B, and a substantial increase in resistance to 1-methyl-3-nitro-1-nitrosoguanidine and proflavine. These results are discussed in terms of known genetic loci implicated in radiation sensitivity and resistance.