Characterization of a new radiation-sensitive mutant, Escherichia coli K-12 radC102.

A new radiation-sensitive mutant, radC , has been isolated. The radC gene is located at 81.0 min on the Escherichia coli K-12 linkage map. The radC mutation sensitized cells to uv radiation, but unlike most DNA repair mutations, sensitization to X rays was observed only for rich medium-grown cells. For cells grown in rich medium, the radC mutant was normal for gamma-radiation mutagenesis, but showed less uv-radiation mutagenesis than the wild-type strain; it showed normal amounts of X- and uv-radiation-induced DNA degradation, and it was approximately 60% deficient in recombination ability. The radC strain was normal for host cell reactivation of gamma-and uv-irradiated bacteriophage lambda; the radC mutation did not sensitize a recA strain, but did sensitize a radA and a polA strain to X and uv radiation and a uvrA strain to uv radiation. Therefore, we suggest that the radC gene product plays a role in the growth medium-dependent, recA gene-dependent repair of DNA single-strand breaks after X irradiation, and in postreplication repair after uv irradiation.