Constitutive error-prone repair at sites of excision repair in Escherichia coli: a re-examination.

No evidence was found for production during incubation in chloramphenicol of a signal capable of inducing a rec-lex function (lysogenic induction) when protein synthesis was restored. The majority of UV-induced mutations to streptomycin resistance require lesions in the DNA and cannot be attributed to untargeted mutator activity. Therefore the loss of photoreversibility of these mutations occurring in the absence of protein synthesis and DNA replication cannot be attributed to the production of a signal for the induction of subsequent rec-lex dependent mutator activity. The simplest interpretation is that they arise as errors at excision sites by the operation of a constitutive pathway.