Scientists have developed two new transgenic grass species that can eradicate the effects of RDX - a toxic compound widely used in explosives since World War II - and neutralise contaminated soil within two weeks. Researchers introduced two genes from bacteria that learned to eat RDX and break it down into harmless components in two perennial grass species - switchgrass (Panicum virgatum) and creeping bentgrass (Agrostis stolonifera). 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 chemical in their leaves or stems. It is 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 Stuart Strand, from University of Washington (UW) in the US. "The grasses could be planted on the training ranges, grow on their own and require little to no maintenance," said Strand. "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," he said. RDX is an organic compound that forms the base for many common military explosives, which can linger in the environment in unexploded or partially exploded munitions. In large enough doses, it has been shown to cause seizures and organ damage, and it is currently listed as a potential human carcinogen. Unlike other toxic explosives constituents such as TNT - which binds to soils and tends to stay put - RDX dissolves easily in water and is more prone to spread contamination beyond the limits of a military range, manufacturing facility or battleground. "Particles get scattered around and then it rains. Then RDX dissolves in the rainwater as it moves down through the soil and winds up in groundwater.
And, in some cases, it flows off base and winds up in drinking water wells," Strand said. Wild grass species do remove RDX contamination from the soil when they suck water up through their roots, but they do not significantly degrade it. So when the grasses die, the toxic chemical is re-introduced into the landscape. Considering the worldwide scale of explosives contamination, only plants are low cost, sustainable solution to cleaning up these polluted sites, said researchers. The study was published in Plant Biotechnology Journal.
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