Synergistic Toxicity by Cadmium and Thiuram

Bioassay is a system for monitoring toxicity of chemicals in the environment via the biological responses of experimental organisms. These responses can be detected by analysis of genome-wide changes in mRNA expression levels using DNA microarray. We applied this system for evaluation of synergistic toxicity by cadmium and thiuram, as this combination showed mutual growth inhibition in yeast. Hierarchical cluster analysis using the mRNA expression profiles suggested the response of yeast to this combination is similar to that seen with cadmium treatment. Functional characterization of induced genes by this combination treatment also suggests the enhanced toxicity of cadmium. This toxicity was observed as the damage to mitochondrial functions which were not observed with either cadmium or thiuram treatments alone. The potential toxicity to mitochondria by this combinational treatment was confirmed as the result of mitochondrial curing. We could evaluate the synergistic toxicity by cadmium and thiuram and show the possible use of transcriptome bioassay for synergistic toxicity. Keywords: stress response This series containes 3 treatment conditions with triplicate experiments from independent biological samples, respectively.