University of Washington engineers have developed transgenic grass species that can eliminate RDX, a toxic compound widely used in explosives that contaminates military bases, battlegrounds and some drinking water wells.
On military live fire training ranges, troops practice firing artillery shells, drop bombs on old tanks or derelict buildings, and test the capacity of new weapons. All those explosives and munitions leave behind toxic compounds that have contaminated millions of acres of U.S. military bases—with an estimated cleanup bill ranging between $16 billion and $165 billion.
In a paper published online in November in Plant Biotechnology Journal, University of Washington and University of York researchers describe new transgenic grass species that can neutralize and eradicate RDX, a toxic compound that’s been widely used in explosives since World War II.
UW engineers introduced two genes from bacteria that learned to eat RDX and break it down into harmless components in Panicum virgatum and Agrostis stolonifera (creeping bentgrass). The best-performing strains removed all the RDX from a simulated soil in which they were grown within less than two weeks and they retained none of the toxic chemicals in their leaves or stems.
It’s the first reported demonstration of genetically transforming grasses to supercharge their ability to remove contamination from the environment. Grasses are hearty, fast-growing, low-maintenance plants that offer practical advantages over other species in real-world cleanup situations.
“This is a sustainable and affordable way to remove and destroy pollutants on these training ranges,” said senior author and UW professor of civil and environmental engineering Stuart Strand, whose lab focuses on taking genes from microorganisms and animals that are able to degrade toxic compounds and engineering them into useful plants.
“The grasses could be planted on the training ranges, grow on their own and require little to no maintenance. When a toxic particle from the munitions lands in a target area, their roots would take up the RDX and degrade it before it can reach groundwater,” Stuart said.
Wild grass species do remove RDX contamination from the soil when they suck water up through their roots, but they don’t significantly degrade it. So when the grasses die, the toxic chemical is re-introduced into the landscape.
Co-authors Neil Bruce and Liz Rylott, biotechnology professor and research scientist, respectively, at the University of York and colleagues had previously isolated enzymes found in bacteria that evolved to use the nitrogen found in RDX as a food source. That digestion process has the added benefit of degrading the toxic RDX compound into harmless constituents.
“Considering the worldwide scale of explosives contamination, plants are the only low-cost, sustainable solution to cleaning up these polluted sites,” said Neil.
The research team also found another unexpected side benefit: Because the genetically modified grasses use RDX as a nitrogen source, they actually grow faster than wild grass species.
Next steps for the UW research team include limited field trials on a military training range to test how the strains perform under different conditions. Wider use would require USDA approval to ensure that the genetic modifications pose no threat to wild grass species.
“I think it would be ecologically acceptable because the genes we’ve introduced degrade real pollutants in the environment and cause no harm,” Stuart said. “From my perspective, this is a useful technology that’s beneficial to the environment and has the potential to remove dangerous legacy contamination from decades of military activity.”
The research was funded by U.S. Department of Defense. Co-authors include UW civil and environmental engineering research techs Ryan Routsong and Quyen Nguyen.
–From a University of Washington press release by Jennifer Langston
December 1, 2016 NewTerrain.