Development of a highly sensitive yeast bioassay for trichothecene detection

Trichothecenes are mycotoxins produced by Fusarium and other genera that can cause serious health problems in humans and livestock. We previously reported 22 trichothecene resistance genes in Saccharomyces cerevisiae, whose deletion conferred high sensitivity to trichothecenes. In this study, we constructed various multiple gene deletion mutants of these resistance genes to develop a sensitive yeast bioassay system for trichothecenes. Among the double and triple null mutants, pdr5Δ erg6Δ rpb4Δ cells showed high sensitivity to T-2 toxin and deoxynivalenol under optimized culture conditions (IC 50 values of 1.5 ng/mL and 1.5 μg/mL, respectively). The disc diffusion test also confirmed the high sensitivity of this mutant to the trichothecenes. This detection system was more sensitive than any other yeast bioassay previously developed. The pdr5Δ erg6Δ rpb4Δ cells detected 1.0 ppm deoxynivalenol in wheat flour and 1.1 ppm deoxynivalenol in wheat grain, which are the advisory level for deoxynivalenol in final wheat products in US and the provisional level for wheat grain in Japan, respectively. Here, we report an easy, inexpensive, and highly sensitive yeast bioassay system to detect trichothecenes.