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Transgenic Tobacco Detoxifies TNT

For more than 150 years, people around the world have made ample use of the explosive trinitrotoluene, otherwise known as TNT. Its use has had unintended consequences, however: the manufacture, storage and disposal of TNT¿which ranks among the most toxic explosives employed by the military¿have left large areas of land contaminated and polluted. So far, effective and affordable cleanup technologies have remained out of reach. But new research suggests that help may come from what might seem an unlikely source: the tobacco plant.

Though tobacco derivatives are known for their toxic effects, the plant itself can apparently serve as a potent detoxifier when equipped with a bacterial enzyme known as nitroreductase (NR). According to a report in the December issue of Nature Biotechnology, tobacco plants genetically modified to express NR can tolerate and degrade TNT at levels comparable with those that characterize contaminated sites.

Building on earlier investigations into phytoremediation, the use of plants for contaminant cleanup, Neil C. Bruce of the University of Cambridge and colleagues created the transgenic tobacco and conducted a series of toxicity experiments. The results were striking. Plants grown on a medium containing high concentrations of TNT removed all of the compound within 72 hours. Moreover, "no TNT was extracted from the transgenic seedlings, indicating that it was either completely transformed or sequestered within the plant in a form that may be unextractable," the authors report.

The researchers are currently examining how these plants perform in TNT-laden soil. If that works, the next step may be to introduce NR into fast-growing, deep-rooted trees like poplars, which, they note, could significantly boost TNT removal in the field. "Such technology," the authors conclude, "may provide the affordable, effective remediation systems that are urgently required."

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