Repair of x-ray-induced single strand breaks in toluenized Escherichia coli cells.

We have used sedimentation in alkali to estimate the repair of X-ray-induced single strand breaks in the DNA of irradiated toluenized Escherichia coli cells. Extensive repair requires no exogenous cofactors except ATP although other individual NTPs (except U) or dNTPs can substitute for ATP. There is no repair in polA or resA cells and since nicotinamide mononucleotide (NMN) inhibits repair in wild type cells we interpret the results as indicating that both ligase and polymerase I are needed for repair but that the amount of any gap filling is small and extensive repair replication is not necessary.