Selective effect of p-aminobenzoic acid on mutagenesis: phenotypic analysis of the Arg+-revertants induced by N-nitroso-N-methylurea in the Escherichia coli K-12 AB1157 strain

According to the phenotypic analysis of Arg+ revertants in Escherichia coli K-12 AB1157, the specific mutational changes in bacterial cells under the action of MNU were registered. True and suppressor mutations of four phenotypic groups were noted. The quantity of mutants induced depended upon the DNA and protein syntheses in bacterial cells. The sublethal concentration of para-aminobenzoic acid markedly (10-50 fold) reduced the rate of mutagenic induction and changed the quantity relations of mutants within phenotypic groups.