Methylmercury demethylation and volatilization by animals expressing microbial enzymes

Mercury is a highly toxic trace metal that readily biomagnifies in food webs where it is inaccessible to current bioremediation methods. Animals could potentially be engineered to detoxify mercury within their food webs to clean up impacted ecosystems. We demonstrate that invertebrate (Drosophila melanogaster) and vertebrate (Danio rerio) animal models can express organomercurial lyase (MerB) and mercuric reductase (MerA) from Escherichia coli to demethylate methylmercury and remove it from their biomass as volatile elemental mercury. The engineered animals accumulated less than half as much mercury relative to their wild-type counterparts, and a higher proportion of mercury in their tissue was in the form of less bioavailable inorganic mercury. Furthermore, the engineered animals could tolerate higher exposures to methylmercury compared to controls. These findings demonstrate the potential of using engineered animals for bioremediation and may be applied to reduce the burden of methylmercury in impacted ecosystems by disrupting its biomagnification or to treat contaminated organic waste streams.