Involvement of genes uvrD and recB in separate mutagenic deoxyribonucleic acid repair pathways in Escherichia coli K-12 uvrB5 and B/r uvrA155.

We compared the ultraviolet radiation-induced reversion of nonsense (lacZ53) and missense (leuB19) mutations in uvrB5, uvrB5 uvrD3, uvrB5 recB21, and uvrB5 uvrD3 recB21 strains of Escherichia coli K-12. Nonsense (trpE65) reversion was also compared in similar derivatives of E. coli B/r uvrA155. The uvrD mutation reduced mutagenesis in very case, but had its main effect in cells ultraviolet irradiated with low fluences (< 0.6 J m-2). The effect of the recB mutation varied; it decreased Leu and Trp reversion, but had little effect on Lac reversion. The effect of the uvrD recB combination was a gross reduction in mutagenesis. Only in the case of Lac reversion was appreciable mutagenesis detected (at fluences > 0.3 J m-2). These results indicate that separate uvrD- and recB-controlled pathways exist for ultraviolet radiation mutagenesis.