Uvm mutants of Escherichia coli K12 deficient in UV mutagenesis. II. Further evidence for a novel function in error-prone repair.

Uvm mutants of Escherichia coli K12 selected for defective UV reversion induction have previously been reported to differ considerably from the UV-reversion-less recA and lexA mutants with regard to survival or mutagenic response to UV, X-rays and alkylating agents. In the present study, the phenotypic characterization of uvm mutants was extended to investigate several cellular processes which also may be related to or involved in UV mutagenesis. Like recA and lexA mutations, the uvm mutations exhibit highly reduced Weigle reactivation and normal host cell reactivation of UV irradiated phage lambda. But unlike recA and lexA, the uvm mutations do not impair genetic recombination, UV induction of prophage lambda or R plasmid-mediated UV resistance and mutagenesis. These phenotypical characteristics and preliminary results of genetic mapping lend further support to the assumption that the uvm site may be a novel locus affecting, apart from the recA and lexA loci, the error-prone repair pathway in E. coli.