Transgenic strains of the nematode Caenorhabditis elegans as biomonitors of metal contamination

Transition metal contamination poses a serious environmental and human heal th threat. The bioavailability of transition metals in environmental sample s can best be assessed with living organisms. A transgenic strain of the fr ee-living soil nematode Caenorhabditis elegans has been engineered for moni toring the bioavailability of metals. A reporter transgene consisting of a fragment of the promoter from the C. elegans metallothionein-2 gene (mtl-2) that controls the transcription of a beta-galactosidase reporter (lacZ) ha s been integrated into the genome of this organism. By using these transgen ic C. elegans, the toxicological response to metals in samples can be quick ly measured with a simple histochemical staining assay. The C. elegans that contain the mtl-2:lacZ transgene provide a more sensitive assay of exposur e to cadmium, mercury, zinc, and nickel than 24-h LC50 assays or those usin g nematodes with heat-shock protein-based reporter transgenes. This study d emonstrates that C. elegans that contain mtl-2:lacZ transgenes can function as sensitive toxicological indicators of metals.