Neil Bruce at the University of York in the U.K. co-authored a paper on the explosive-slurping Arabidopsis plant, which also appears this week in PNAS.
Several years ago the biologist and colleagues found a soil microorganism that had adapted to use the nitrogen found in RDX to grow.
This microbe has since been found at RDX-contaminated sites around the world.
"But whilst you can find these microorganisms there, they clearly aren't breaking down the explosive fast enough before it migrates through the soil and contaminates groundwater," Bruce said.
Plants are well known for soaking up certain chemicals from soil, air, and groundwater and breaking them down into harmless components, he said. But no known plant naturally breaks down RDX.
So Bruce and colleagues combined the enzyme system from the soil microbes with Arabidopsis, a model plant for scientific studies because its genetic changes are easily observed (get a genetics overview).
Their first successful attempt was published in the January 2006 issue of the journal Nature Biotechnology. The new research published this week in PNAS documents the plants' superior performance.
"We've managed to identify the complete systems that allow this enzyme to work, and we've got both components of this enzyme system successfully expressed and working in Arabidopsis," Bruce said.
His team is now collaborating with researchers at the University of Washington in Seattle to develop grasses and trees more suited to removing RDX from contaminated soils at military bases around the world.
Contaminant Cleaning
Stuart Strand, a research professor in the College of Forest Resources at the University of Washington, leads the collaboration with Bruce's team and is also a co-author of the paper on transgenic poplar trees.
That study used a similar technique to enhance the ability of poplar trees to remove a host of carcinogens from the environment.
In this case, the team inserted a gene that produces a contaminant-cleaning enzyme found in rabbit livers into the poplar trees.
Although poplars already naturally remove contaminants from the environment, the rabbit liver enzyme speeds up the process.
For example, the altered poplars removed trichloroethylene—a heavily used industrial degreaser—53 times faster than nonaltered trees, lead study author Doty noted.
The trees also more quickly removed carcinogens such as chloroform and vinyl chloride from the ground and benzene from the air.
And while control plants removed none of the industrial solvent trichloroethylene from the air, the altered trees removed 79 percent of the chemical during a week-long experiment.
Doty added that poplars grow for several years before flowering, and fallen branches do not take root in soil. As such, the trees could be harvested before their seeds germinate and spread their genes.
But Jane Rissler, of the Union of Concerned Scientists, cautioned that promises of safe bioremediation techniques seldom come to fruition.
"There have been so many promises in the past 20 years and so few products," she said, "and phytoremediation is another promise that hasn't been met."
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