[Induction of SOS function in Escherichia coli after exposure to various types of chemical mutagens]

On the basis of the SOS-chromotest which was developed by the authors earlier, the minimum time required for expression of the SOS-response is shown to be 15 min, the maximum being recorded 2 h later. An assay of induction of the SOS-response to the mutagens which act on DNA via various mechanisms (e. g., UV-irradiation, mitomycin C, nalidixic acid, nitroso-methylurea and acridine orange) revealed that all the mutagens under study caused induction of the SOS-response. Analysis of efficiency of SOS induction under the action of a mixture of formaldehyde with various amino acids has shown that arginine, asparagine and, especially, cysteine decrease the level of the SOS-response induction. This fact suggests an opportunity for using the SOS-chromotest not only to identify the mutagens and cancerogens, but also to screen the agents for their antimutagenic activity. The study of the SOS-response in the cells which are deficient in genes for repair and recombination has shown that induction is significantly suppressed in the mutants recA, lexA and recF; it is not modified in sbcB mutants and is significantly increased in the mutant lines recBC, uvrB and, particularly, in the double mutant recBCsbcB.