Fate of thymine-containing dimers in the deoxyribonucleic acid of ultraviolet-irradiated mutator T1 Escherichia coli transfuctants

In order to determine whether a relationship generally exists between the mutator property (mutT1) and repair of ultraviolet (UV) irradiation damaged DNA, we performed spontaneous mutation rate and UV-survival determinations without and with acriflavin (4 μg/ml) in P1 phage mediated mut T1 Escherichia coli transductants. The strains constructed were assumed to be cosigenic except for the mutator factor. The mutT1 uvrA, uvrB or exrA transdunctants had mutation rates similar to the donor strain. Double mutants containing mutT1 and uvrB or exrA had the same level of UV survival as the parent with the same mutator phenotype. Mutator strains were normal for host-cell reactivation of UV-irradiated phage T1, and phage lambda was UV-inducible. The fate of UV-induced thymine-containing dimers in the deoxyribonucleic acid (DNA) of mutT1 transductants was investigated. Dark repair of pyrimidine dimers is equally sensitive in the nonmutator and mutator Hcr⁺. During incubation in the dark, dimers were excised to the same extent from the DNA of the Hcr⁺ mutator and nonmutator transductants but remained in the DNA of the Hcr^? mutant.