Differential mutagenic response of Salmonella typhimurium to the plant-metabolized organophosphorus insecticides, phoxim and azinphos methyl.

The plant cell/microbe coincubation assay was used to analyze organophosphorus insecticide activation. Salmonella typhimurium strains TA98 and TA100 were exposed to several concentrations of the pesticides phoxim and azinphos methyl with and without TX1 cell line of Nicotiana tabacum activation. When the bacterial strains were treated directly with phoxim, mutagenic activity increased significantly. In contrast, no mutagenic activity was detected with plant activation. Azinphos methyl inhibited the growth of Salmonella strains without plant activation. The coincubation with N. tabacum increased mutagenic activity significantly. These findings and those obtained in animals demonstrated that azinphos-methyl was an indirect mutagen or pro-mutagen activated by the plant metabolism.