Bioremediation of Soils Contaminated with Toxic Metals Using Transgenic Plants Overexpressing a Cation Transport Pump

Background: There are currently few satisfactory choices for the rectification of toxic or radioactive metal contamination of soils. On a small scale, contaminated areas may be restored by physical removal of surface layers, followed by appropriate disposition (usually remote burial) of the material and re-landscaping to restore the site. On a large scale, this approach is infeasible, and the alternative is to abandon the land for a prolonged period or permanently, restricting access or uses. The current invention offers a means of safely and economically depleting soils of metal contaminants through a bioremediation approach that preserves the original structure of the land and eventually restores its utility, even when many square miles are involved.

Technology Description : A cDNA encoding a novel cation pump having broad specificity has been isolated and characterized from a wheat root library. Clones incorporating this ion uptake pump can be transferred to species of plants having deep root systems and rapid growth on a variety of soils. With the ion pump over-expressed throughout the plant tissues, these transgenic plants are capable of accumulating a variety of toxic metals from the soil and concentrating them on leaf surfaces or internally.

Metal ions targeted by this system include: cadmium, lead, zinc, nickel, antimony, mercury, silver, tin, copper, cobalt, cesium, strontium, radium, uranium and osmium. Beryllium and aluminum are not effectively transported by this system, nor are metal ions existing as tightly-bound complexes. By a repetitive process of extensive planting, harvesting and incineration of the contaminated biomass, the metal toxicant in the soil can be reduced to acceptable levels.

Advantages: This method of bioremediation is of particular use in removing heavy metals and certain radioactive metals that could be associated with industrial or nuclear mishap contamination of wide areas. Bioremediation systems using plants are often restricted to certain species -- this approach allows the combining of the most suitable plant for the task/environment with overexpression of the high-capacity metal pump.

Case Number: SD1996-102

Inquiries To: invent@ucsd.edu