MUTATIONAL SPECTRUM OF REVERTANTS IN THE HISD3052 ALLELE OF SALMONELLA-TYPHIMURIUM INDUCED BY HYDROGEN PEROXIDE-ACTIVATED BENZIDINE

Benzidine is mutagenic in a modified Ames (Salmonella typhimurium) ass ay, which uses hydrogen peroxide-dependent peroxidative activation. Th e mutational specificity of benzidine was investigated in tester strai n TA98, which reverts by frameshifts of the hisD3052 allele. The most frequently observed mutation is a deletion of two bases from a (CG), r un. This deletion was elevated in frequency among benzidine-induced re vertants, relative to spontaneous revertants. Many other mutations wer e also observed, including additions, deletions, and complex events. O nly small frameshifts were observed among the benzidine-induced revert ants, whereas some larger deletions were observed among the spontaneou s revertants.