Inhibition of excision repair without influence upon UV-sensitivity and UV-mutability in Escherichia coli B/r Hcr+.

Pre-irradiation starvation of exponentially growing Escherichia coli B/r Hcr+ thy-try- strain for thymine and tryptophan causes inhibition of pyrimidine dimer excision from ultraviolet damaged cells DNA. This inhibition of excision repair has not resulted in increasing ultraviolet sensitivity nor in increasing frequency of ultraviolet induced tryptophan revertants. The possible mechanisms of the non-excision repair in the prestarved cells, which is at least as accurate and effective as the whole dark repair in exponentially growing cells, are discussed.