[Mechanism of reactivating Escherichia coli inactivated by ultraviolet light with cell extracts of propionic acid bacteria].

Two mechanisms of reactivation of UV-inactivated Escherichia coli cells--photoreactivation (PhR) and reactivation by the dialysates of propionic acid bacteria--are shown to be different but not completely additive. PhR displays an insignificant negative effect on the reactivation by active substances (peptides) of the dialysate, whereas reactivation by dialysate inhibits PhR. The maximal reactivation can be attained under complete PhR followed by the protective action of dialysate. The dialysate protects UV-irradiated E. coli cells with PolA, UvrA, and RecA mutations and Salmonella typhimurium TA 100 (UvrB) cells and also exerts an antimutagenic effect on S. typhimurium TA 100. Protection by dialysate is suggested to be due to restoration of the cell division mechanism damaged by UV irradiation.