Survival and induction of recA protein in mitomycin C-treated Escherichia coli rec, lex, or uvr strains.

The capability to synthesize recA protein has been tested for Escherichia coli treated with mitomycin C. recA protein was assayed using an immunoradiometric assay (Paoletti, C., Salles, B., and Giacomoni, P. U. (1982) Biochimie 64, 239-246). Mitomycin C-treated wild type E. coli can express recA gene in a similar quantitative fashion, independently of the growth media used in this work; glucose did not inhibit induction of recA protein in cells growing in synthetic media. Wild type E. coli recovering from energy starvation displays a similar qualitative capability to induce the synthesis of recA protein independently of the stage of growth at which the cells are treated with the drug. At midexponential phase, the cells appear to have an enhanced capability to synthesize recA protein. The relationship between survival and capability to synthesize recA protein was explored for E. coli lex, rec, and/or uvr mutants, after treatment with mitomycin C. A good correlation was found, except for a recB mutant and for an ethidium-sensitive strain, both able to produce as much recA protein as the wild type but 100-fold more sensitive to the drug. A similarly satisfactory correlation was found when plotting the survival after UV irradiation versus the capability of synthetizing recA protein with the exception of an uvrA strain and of a lexA strain.