Discriminated induction of SOS functions in Escherichia coli by alkylating agents.

Treatment of Escherichia coli with the alkylating agents diethyl sulphate, ethyl methane-sulphonate and N-methyl-N'-nitrosoguanidine produces a different pattern of expression of SOS functions. There is a full induction of recA-dependent inhibition of cell respiration, a slight induction of lambda prophage, and no inhibition of cellular division. In a comparative study with bleomycin, an agent which is able to induce these three SOS functions, we have also shown that the differences in expression of SOS functions are not due to any variation in the pattern of DNA synthesis, or DNA degradation after treatment with alkylating agents. These results suggest that the kind of damage induced in the DNA may be important in determining which SOS function is expressed.