A minor pathway of postreplication repair in Escherichia coli is independent of the recB, recC and recF genes

Abstract

After ultraviolet (UV) irradiation, an Escherichia coli K12 uvrB5 recB12 recF143 strain (SR1203) was able to perform a limited amount of postreplication repair when incubated in minimal growth medium (MM), but not if incubated in a rich growth medium. Similarly, this strain showed a higher survival after UV irradiation if plated on MM versus rich growth medium (i.e., it showed minimical medium recovery (MMR)). In fact, its survival after UV irradiation on rich growth medium was similar to that of a uvB5 recA56 strain, which does not show MMR or postreplication repair. The results obtained with a uvB5 recF332::Tn3 Δ recBC strain and a uvB5 recF332::Tn3 recB21 recC22 strain were similar to those obtained for strain SR1203, suggesting that the recB21 and recF143 alleles are not leaky in strain SR1203. The treatment of UV-irradiated uvB5 recB21 recF143 and uvrB5 recF332::Tn3 δ recBC cells with rifampicin for 2 h had no effect on survival or the repair of DNA daughter-strand gaps. Therefore, a pathway of postreplication repair has been demonstrated that is constitutive in nature, is inhibited by postirradiation incubation in rich growth medium, and does not require the recB recC and recF gene products, which control the major pathways of postreplication repair.