Development of a Bacterial Hyper-sensitive Tester Strain for Specific Detection of the Genotoxicity of Polycyclic Aromatic Hydrocarbons

Abstract

Benzo[a]pyrene (B[a]P), one of polycyclic aromatic hydrocarbons (PAHs), is a ubiquitous environmental pollutant and a potent mutagen and carcinogen. To sensitively detect the genotoxicity of PAHs in complex mixtures extracted from environmental pollutants, Salmonella enterica serovar Typhimurium (S. typhimurium) strain YG5161 is engineered by introduction of plasmid pYG768 carrying the dinB gene encoding Escherichia coli DNA polymerase IV into standard Ames tester strain S. typhimurium TA1538 (Matsui et al., DNA Repair in press). Strain YG5161 exhibits higher sensitivity to the genotoxic-ity of B[a]P and other PAHs than do strain TA1538 and TA98. As the conventional Ames tester strains do, however, strain YG5161 also detects the mutagenicity of aromatic amines and nitroaromatics with high sensitivity, which may veil the genotoxicity of PAHs in complex mixtures. S. typhimurium possesses strong enzyme activities of nitroreductase and O-acetyltransferase, which mediate the metabolic activation of aromatic amines and nitroaromatics and enhance the potent genotoxicity. In this study, we disrupted the nfsB and oat genes encoding the activation enzymes in strain TA1538 to reduce the cross sensitivity, and introduced plasmid pYG768 into the DnfsB Doat strain. The resulting strain YG5185 retained similar high mutability to various chemicals including PAHs as did strain YG5161 and substantially decreased the sensitivity to 1-nitropyrene, 1,8-dnitropyrene and 2-amino-6-methyldipyrido[1,2-a:3?,2?-d]imidazole (Glu-P-1). We propose that the novel tester strain YG5185 is useful to speciˆcally and sensitively detect the genotoxic PAHs in complex mixtures from various polluted environmental sources.