Phenotypes of UV-sensitive uvrD3, recL152, and uvrE15 mutants of Escherichia coli.

The mutations uvrD3, uvrE156, and recL152 increase UV sensitivity in Escherichia coli and are closely linked. There is a disagreement as to whether uvrD3 and uvrE strains have distinctive phenotypes. Comparison of strains isogenic except for the uvrD3, uvrE156, and recL152 mutations showed that only the uvrD3 mutation greatly decreased the host cell reactivation of phages T1 and lambda vir and the repair of methyl methanesulfonate (MMS) damage. Only the uvrE156 mutation increased mutation rates. Excessive DNA degradation following UV-irradiation occurred only in the uvrD3 mutant. MMS-resistant mutants of a uvrD3 strain, resulting from mutations closely linked to uvrD3, were still UV-sensitive and fell into two classes: mutator (UvrE--like) and non-mutator. Spontaneous mutator mutants having the UvrE- phenotype were also found in aged uvrD3 cultures. The uvrD3 mutation in heterogenotes was partially dominant.