Effects of chloramphenicol on the postreplication repair and sister recombinational DNA exchanges in ultraviolet-irradiated Micrococcus luteus.

The filling of about one third of postreplication DNA gaps in u.v.-irradiated Micrococcus luteus ATCC 4698 is blocked by chloramphenicol (CA) added just before irradiation. Addition of CA 15 min after u.v.-irradiation does not prevent the complete repair of the gaps. U.v.-sensitive M. luteus mutants (ML 6 and ML 15) are identified as defective in different steps of inducible postreplication DNA repair (PRR). PRR in unexcising M. luteus strain G7 is accompanied by the transfer of about 20% of pyrimidine dimers from parental to daughter DNA strands, which indicates the existance of recombinational pathway of PRR. Recombinational PRR in M. luteus is not inhibited by CA.