Photomutagenicity of thiabendazole, a postharvest fungicide, in bacterial assays.
We investigated the photomutagenicity of thiabendazole (TBZ), a postharvest fungicide commonly used on imported citrus fruits. Using UVA light (320-400 nm), we irradiated bacterial cultures with or without TBZ in a 24-well multiplate. UVA-irradiation without TBZ was not mutagenic to the tester strains, nor was unirradiated TBZ. TBZ was strongly photomutagenic in Escherichia coli WP2uvrA and WP2uvrA/pKM101 strains, weakly photomutagenic in Salmonella typhimurium TA100 and TA98, and not photomutagenic in S. typhimurium TA1535 and TA1538. The photomutagenicity of TBZ was more evident in WP2uvrA/pKM101, which carries the trpE65 ochre mutation (TAA), than in TA100, which carries the hisG46 missense mutation (CCC). In E. coli WP3101-WP3106 and the corresponding pKM101-containing strains, photoactivated TBZ induced predominantly G:C-->A:T transitions and A:T-->T:A transversions. In the plasmid-containing strains only, TBZ induced a moderate number of A:T-->G:C transitions and a few A:T-->C:G and G:C-->T:A transversions. The observation that UVA-irradiated TBZ mutated both G:C and A:T basepairs may explain why WP2uvrA/pKM101 was more sensitive to its mutagenicity than TA100. TBZ that was irradiated before it was added to the WP2uvrA/pKM101 cells was not photomutagenic, which suggests that the photomutagenic products of TBZ were unstable or rapidly reacted with other molecules before being incorporated into cells.
Watanabe-Akanuma
Mie
M
Institute of Environmental Toxicology, Tokyo, Japan. akanuma@iet.or.jp
Ohta
Toshihiro
T
Yamagata
Hideo
H
D000969:Antinematodal Agents / Q000633:toxicity*; D004249:DNA Damage / Q000187:drug effects / Q000528:radiation effects; D004269:DNA, Bacterial / Q000187:drug effects / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000528:radiation effects*; D006639:Histidine / Q000378:metabolism; D009152:Mutagenicity Tests / Q000379:methods*; D009153:Mutagens / Q000633:toxicity; D009154:Mutation; D010957:Plasmids; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000235:genetics / Q000528:radiation effects*; D013827:Thiabendazole / Q000633:toxicity*; D014364:Tryptophan / Q000378:metabolism; D014466:Ultraviolet Rays
D000969:Antinematodal Agents; D004269:DNA, Bacterial; D009153:Mutagens; D006639:Histidine; D014364:Tryptophan; D013827:Thiabendazole