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J Bacteriol. 1972 February; 109(2): 475-483
Copyright © 1972 American Society for Microbiology. All Rights Reserved.

Deoxyribonucleic Acid Damage by Monofunctional Mitomycins and Its Repair in Escherichia coli

Faculty of Pharmaceutical Sciences, Kyushu University, Katakasu, Fukuoka, Japan

ABSTRACT

Exposure of Escherichia coli to the antibiotic mitomycin C (MTC) at a concentration of 0.5 µg/ml caused cross-linkage between complementary strands of deoxyribonucleic acid (DNA). Derivatives of mitomycin, 7-methoxymitosene (7-MMT) and decarbamoyl mitomycin C (DCMTC), at a level as high as 20 µg/ml formed no cross-links between DNA strands. Ultraviolet light-sensitive mutants of E. coli K-12 bearing uvrA, uvrB, uvrC, or recA mutations were more sensitive to the lethal action of 7-MMT and of DCMTC than was the wild-type strain. Treatment of wild-type cells with these antibiotics resulted in the production of single-strand breaks in DNA, which were repaired upon incubation in a growth medium. Such breaks in DNA were not produced in the uvrA and the uvrB mutants. In the uvrC mutant, single-strand breaks were produced by 7-MMT or by DCMTC, but these breaks were not repaired upon incubation. These results are discussed in connection with the mechanism for removal of pyrimidine dimers in ultraviolet-irradiated bacteria.