Varieties of common grass have been genetically engineered to break down toxic chemicals released into the environment by years of military testing. The results demonstrate the potential to decontaminate areas polluted by hazardous by-products.
Published in Plant Biotechnology Journal, the study focused on two chemicals, RDX and TNT, which are produced by military testing, manufacturing and the decommissioning of explosives. More than 100 military bases and explosive manufacturing locations in the USA are contaminated with these compounds. The cost of decontamination of these sites has been estimated to be between 16 and 165 billion US dollars.
As for the chemicals, human exposure to TNT can result in hepatitis and RDX is a neurotoxin which can cause seizures in humans and animals. Both are considered potential carcinogens by the Environmental Protection Agency (EPA).
The plants were produced by incorporating genes from bacteria able to produce enzymes that degrade and transform these toxic chemicals. Specific genes were isolated from a strain of the bacteria Rhodococcus rhodochrous, found to be able to grow in conditions where RDX is the sole nitrogen source. Similarly, the Enterobacter cloacae bacteria contains one of these genes, and is able to transform, and detoxify TNT. Expression of these genes together, enabled these plants to remove RDX and TNT from soil samples.
The researchers, from the University of Washington, created transgenic versions of the two most common grasses found on military ranges. Grasses are preferred candidates for this approach as they are fast growing and require little to no maintenance. Wild grasses have already been shown to take up RDX from groundwater, but these plants lack the ability to degrade the toxic compounds and ultimately die, releasing the contaminants back into the environment.
The grasses were then tested, and researchers found the best performing strains could remove all traces of RDX from the soil within two weeks, with no toxic products remaining in the plants themselves. Furthermore, a surprising benefit is that since the plants utilize these toxic compounds as a nitrogen source, they actually grow faster than wild type strains.
The next step for the researchers is to see how the plants perform in a real-world setting. The plan is to test the grasses on military training ranges but more widespread use in the future will require demonstrations that these genetic modifications don’t pose any threat to wild grass populations. If approved however, this advancement could have great implications for environmental efforts at decontamination.
Tim Davies is studying for a PhD in neural stem cell biology
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