PHYTOREMEDIATION OF MERCURY-POLLUTED AND METHYLMERCURY-POLLUTED SOILSUSING GENETICALLY-ENGINEERED PLANTS

Inorganic mercury in contaminated soils and sediments is relatively im mobile, though biological and chemical processes can transform it to m ore toxic and bioavailable methylmercury. Methylmercury is neurotoxic to vertebrates and is biomagnified in animal tissues as if is passed f rom prey to predator. Traditional remediation strategies for mercury c ontaminated soils are expensive and site-destructive. As an alternativ e we propose the use of transgenic aquatic, salt marsh, and upland pla nts to remove available inorganic mercury and methylmercury from conta minated soils and sediments. Plants engineered with a modified bacteri al mercuric reductase gene, merA, are capable of converting Hg(II) tak en up by roofs to the much loss toxic Hg(O), which is volatilized from the plant Plants engineered to express the bacterial organomercurial lyase gene, merB, are capable of converting methylmercury taken up by plant roots into sulfhydryl-bound Hg(II). Plants expressing both genes are capable of converting ionic mercury and methylmercury to volatile Hg(O) which is released into an enormous global atmospheric Hg(O) poo l. To assess the phytoremediation capability of plants containing the merA gene, a variety of assays were carried out with the model plants Arabidopsis thaliana, and tobacco (Nicotiana tabacum).