Document: AND-3-62-3

Development of a strategy for the plant-mediated remediation of mercury polluted soils and sediments.

HEATON, A.* ¹, S.P.BIZILY ¹, Y.J.LI ¹, C.L.RUGH ², R.B.MEAGHER ¹ and B.L.HAINES ¹

University of Georgia, Athens, GA 30602 ¹
Michigan State University, ²

Abstract:
Industrial practices have released mercury into many environments that now require remediation. Current remediation strategies are costly, site-destructive and may cause a temporary but significant increase in the mobilization of mercury from contaminated sites. We are developing an alternative mercury remediation strategy, phytoremediation. Phytoremediation is the use of plants to extract, sequester, or detoxify environmental contaminants. We have engineered several plant species with bacterial mercury resistance genes merA and/or merB. MerB enables plants to extract organomercurials (e.g. methylmercury) from growth substrates and convert them to less toxic Hg(II). MerA enables plants to chemically reduce this Hg(II) product or soil-absorbed Hg(II) directly from polluted soils to less toxic Hg(0) which is volatilized from the system. We have been assessing the ability of these plants to remove the more toxic forms of mercury from various growth substrates (e.g. semisolid growth agar, hydroponics media, or soils) and detoxify these forms to Hg(0). The hypothesis for this work is that merA/merB plants can remediate soils and sediments contaminated with ionic or organic forms of mercury. Preliminary results show that transgenic plants have a strong survival advantage over wildtype counterparts when grown on mercury-contaminated substrates. An extension of this work will be the engineering of a novel plant which should be able to remove mercury from the soil and store it in aerial tissues for later harvest and hazardous waste disposal. The hypothesis for this aspect of the study is that plants engineered to express the mer genes in roots but not in aboveground tissues, and which express elevated levels a of metal-binding proteins in stems and leaves can extract a substantial quantity of mercury from growth substrates and store it in aboveground tissues. A simulation of this genetically-engineered plant was created by grafting wildtype aboveground tissues to merA roots. The model plant loads substantially more mercury from spiked hydroponics media into aboveground tissues than do ungrafted wildtype or merA plants.

Keywords: mercury pollution, phytoremediation, genetic engineering, grafting, hydroponics

This abstract is being presented at: 3:30 PM in session:
Poster Session #15: Nutrient Cycling.