Strains of Escherichia coli hypersensitive to representative carcinostatic and carcinogenic agents.

Abstract

An attempt was made to construct a strain of E. coli with triple mutations in genes, uvrA, ruv and tolC (same as mtcB) which might be suitable for detection of substances having carcinostatic activity and/or carcinogenic potency. The UV-sensitive uvrA mutant is defective in an initial step of excision of damages on DNA produced by UV or chemicals acting like UV, and is also sensitive to these substances. The ruv mutant, although normal in ability for excision repair for DNA damage, is sensitive to UV, MMC [mitomycin C] and nalidixic acid. The uvrA ruv strain is more sensitive to UV irradiation than the strain with single mutation in the corresponding gene. The mtcB mutant, which was originally isolated as an MMC-sensitive mutant, seems to be identical to the tolC mutant, since it is resistant to colicin E1 and sensitive to sodium dodecylsulfate, sodium deoxycholate, basic dyes and bleomycin. The strain with triple mutations in uvrA, ruv and tolC (mtcB) was prepared. The compounds, bleomycin, MMC, carboquone and adriamycin, which are clinically used in Japan as carcinostatic agents, and 4-nitroquinoline-1-oxide and furylfuramide, both of which are known as potent carcinogens and mutagens, were used for testing the validity of the present assay system.