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My latest blog on our field trial of explosive-eating GM swtichgrass here
A GM approach using plants to detoxify explosives
On military training ranges, the containment of explosives is a significant environmental problem, and concern.
Our studies, in collaboration with ERDC-CRREL, and the Department of Civil and Environmental Engineering, University of Washington, Seattle, WA. aims to understand and clean-up this pollution.
On military training ranges, these two pollutants are of concern:
The problems with TNT:
A synthetic chemical not found in nature
Toxic and causes cancer
Does not readily break-down in the environment
Plants have only a very limited ability to detoxify TNT (plants with the ability to degrade TNT have not been found)
A co-pollutant with RDX
Sticks to the soil, and does not wash easily into ground water
One way to think about TNT is as a kind of "toxic Velcro". TNT binds tightly to the soil particles and is not readily washed through the soil. Particularly toxic to plants, the accumulating "toxic Velcro" reduces the ability of plants to establish and grow in the contaminated soil.
The problems with RDX:
A synthetic chemical not found in nature
Toxic
Does not readily break-down in the environment
Plants have only a very limited ability to breakdown RDX
A co-pollutant with TNT
Washes easily into ground water threatening drinking water supplies
A perhaps rather disgusting, but certainly memorable, way to remember the problem with RDX is that the effect of RDX in the soil is a little like the effect of a vindaloo curry on your digestive system: RDX rapidly travels through the soil!
The accumulation of RDX in a sole source aquifer under the Massachusetts Cape Cod military training range was at high enough levels for the US Environmental Protection Agency to stop the use of live munitions on the ranges (Rylott EL and Bruce NC (2009) Plants disarm soil: engineering plants for the phytoremediation of explosives. Trends Biotechnol. 27: 73-81).
While plants have only limited abilities to deal with these explosives, bacteria, with their fast generation times, have evolved genes encoding enzymes that are able to detoxify TNT and break-down RDX.
From the bacterium Enterobacter cloacae a nitroreductase (NR) with the ability to transform TNT to less toxic intermediates have been isolated.
From the bacterium Rhodococcus rhodochrous 11Y, an enzyme, XplA, and a helper partner, XplB are able to trigger the break-down of RDX
We have transferred these genes into Arabidopsis, a model plant species for laboratory studies.. The picture below illustrates the success of Arabidopsis plants engineered with explosives-detoxifying genes. When Arabidopsis plants contain both NR and XplA, they are able to withstand the toxicity of TNT, enabling RDX to be broken down. A bonus, is that the nitrogen derived from the degradation of RDX is used as to fuel growth.Not fertilisers to make explosives, but explosives to make fertilisers!
More recently, we have moved this technology into grass species such as switchgrass (Panicum virgatum). Switchgrass is a suitable species because it is native to US military training ranges in temperate regions and has a deep, penetrating root system. Importantly for the military, switchgrass is robust enough to withstand heavy armoured vehicles (tanks) driving over it, and it is fire resistant (a potential hazard on live-firing ranges).
19 January 2016
Here are some photos of our field trial site in the US. We have a 'subject-to-site-visit' permit, so should be ready to start the trial this spring.
Digging the sub plots (left). That's me fixing one of the lysimeters on a sub plot (right).
Aerial view of the plot, it's near a runway and the pilots are now using it as a navigational feature! (left). Cross section showing design of a sub plot (right)
Here are some photos of the plots in July 2017:
This work is funded by the US and UK military (ESTCP, SERDP DSTL), and BBSRC
https://www.serdp-estcp.org/
https://www.gov.uk/government/organisations/defence-science-and-technology-laboratory
Details on this work have been presented at a number of conferences, a UK PlantSci one can be viewed here:
Presentation at UK PlantSci Conference, York
"Plant Cillit Bang! And the dirt is gone! Using TNT to understand detoxification of organic pollutants by plants"
Watch video on the Journal of Experimental Botany website
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