Ultraviolet light-induced recovery in Escherichia coli of gamma-irradiated bacteriophage DNA.

The susceptibility to inducible SOS repair of damage produced by direct and indirect action of ..gamma.. rays in single-stranded and replicative-form (RF) phi X174 DNA has been investigated. A sector of inducible repair was found for all irradiation conditions examined when the phage-producing ability of both forms of irradiated DNA was determined by transfection into calcium-treated Escherichia coli AB1157 which previously had been exposed to ultraviolet (uv) light. The amount of inducible recovery was dependent upon the irradiation condition of the DNA, but for a given condition the extent of inducible repair was the same for both single-stranded and RF DNA molecules. From these results we conclude that different irradiation conditions yield damages which vary in their susceptibility to inducible repair and that these damages possibly are repaired with equal efficiency in both single-stranded and double-stranded DNA by a common mechanism.