[Carminomycin induction of single-stranded DNA breaks in Micrococcus luteus cells]

The effect of carminomycin, an amtitumor antibiotic from the anthracycline group on DNA of M. luteus cells was studied. It was shown that carminomycin induced one-thread breaks in DNA. The antibiotic effect was proportional to its concentration and depended on the time of the cell exposure. When the incubation time with carminomycin was longer, there was observed disappearance of a significant part of the breaks. The lower was the antibiotic concentration, the rapider was the process, especially after removal of the antibiotic from the medium. Induction of the one-thread breaks by carminomycin in DNA of the cells of the mutant strain DB-7 of M. luteus was more difficult than in that of the cells of the wild type strain which was indicative of the enzymatic character of most of the breaks and of a special role of UV-endonuclease of M. luteus in this process. On the basis of carminomycin hypersensitivity of the mutant it was concluded that the above enzyme was probably involved in reparation of the DNA damages induced by carminomycin. No two-thread breaks induced by the antibiotic were detected.