Conjugation-dependent enhancement of induced and spontaneous mutation in the lacI gene of E. coli.

The frequency of lac mutations induced in an F'lacIS plasmid, transferred by conjugation from UV-irradiated, excision-deficient donors to excision-deficient, delta pro lac recipients, is 2-3 fold higher than that typical of nonmating cells which contain the plasmid. These additional induced mutations can probably be ascribed to errors made during the first, or repliconation, synthesis that takes place in the recipient during the course of plasmid transfer. We also find that spontaneous mutation rates are enhanced in conjugating cells, indicating that fewer errors are corrected, or more made, during transfer replication.