Effects of chloramphenicol and caffeine on postreplication repair in uvr A- umuC- und uvrA- recF- strains of Escherichia coli K-12.

Postreplication repair and its inhibition by chloramphenicol and caffeine, as seen in alkaline sucrose gradients, were compared between a uv non-mutable strain uvrA- umuC- and normally mutable strains uvrA- recF- and uvrA- umu+rec+ of Escherichia coli K-12. The uvrA- umuC- strain performed postreplication repair as efficiently as the parental strain, while the repair in uvrA- recF- strain was dependent on UV dose. Both chloramphenicol and caffeine inhibited postreplication repair to an equal extent of about 25%, and 10%, respectively, in all three uvrA- strains of umuC36, recF- and umu+rec+. These observations suggest that postreplication repair is largely not responsible for UV mutagenesis.