Indirect Ultraviolet-Reactivation of Phage λ
Abstract
When an F- recipient Escherichia coli K12 bacterium receives Hfr or F-lac + DNA from an ultraviolet-irradiated donor, its capacity to promote DNA repair and mutagenesis of ultraviolet-damaged phage λ is substantially increased.
We call this phenomenon indirect ultraviolet-reactivation, since its features are essentially the same as those of ultraviolet-reactivation; this repair process occurs in pyrimidine dimer excision-deficient strains and produces clear plaque mutations of the restored phage. Moreover, this process is similar to indirect ultraviolet-induction of prophage λ, since it is promoted by conjugation. However, contrarily to indirect induction, it is produced by Hfr donors and occurs in recipients restricting the incoming ultraviolet-damaged donor DNA.
The occurrence of indirect ultraviolet-reactivation provides evidence for the existence in E. coli of an inducible error-prone mechanism for the repair of DNA.
