Large swaths of U.S. military land are covered with munitions components, including the explosive chemical RDX. This molecule is toxic to people and can cause cancer. It also doesn’t naturally break down and can contaminate groundwater.

Now researchers have genetically engineered a grass commonly used to fight soil erosion so that it can remove RDX from the soil, according to a May 3 in Nature Biotechnology.

The team, which includes researchers from the 91探花, demonstrated that over the course of three years, a genetically engineered switchgrass could break down RDX in plots of soil at a military range. This is the first time researchers have used a genetically engineered plant in the field to remove pollutants that are resistant to degradation, the team said.

“Our lab’s expertise is in genetic engineering useful plants 鈥� such as grasses and houseplants 鈥� so that they can degrade pollutants,” said co-author , a 91探花research professor emeritus in the civil and environmental engineering department. “The big goal here is to prevent cancer-causing chemicals from contaminating groundwater beneath active, live-fire training ranges by planting these grasses in and around target areas.”

RDX is designated as a priority pollutant by the U.S. Environmental Protection Agency and is of significant and increasing public concern.

“The recalcitrance of RDX to degradation in the environment, combined with its high mobility through soil and groundwater, mean that plumes of toxic RDX continue to spread below these military sites, threatening drinking water supplies,” said senior author , a biology professor at the University of York in the United Kingdom.

Because of the scale of explosives pollution, there is considerable interest in developing sustainable remediation strategies, such as using plants to help break down toxic compounds, the researchers said.

To create these grasses, the researchers inserted two genes from a soil bacterium that has evolved to break down RDX into switchgrass (Panicum virgatum).

Then the team tested the plants at a military range in New York state. The researchers compared three different conditions 鈥� no plants, non-genetically engineered grass and the engineered grass 鈥� on 27 plots containing RDX at a typical concentration found in contaminated sites.

After three years, the excess water coming off the plots with the engineered grass contained lower levels of RDX compared to the other two types of plots. In addition, the engineered plants had little or no RDX in their tissues compared to the wild-type plants, suggesting that these grasses were taking up and metabolizing this chemical.

“We estimate that grass would need to be grown for several years on most sites with contaminated soil, but less contaminated sites could be remediated more quickly,” Strand said. “This technology would be very cheap compared to alternative methods.”

Before this system is ready to be used at contaminated sites, researchers will need to perform biosafety experiments to check how these engineered grasses would affect native plants, the team said.

“We demonstrated that by inserting these genes into switchgrass, the plant then had the ability to degrade RDX to non-detectable levels in the plant tissue,” said co-author , a biology lecturer at the University of York.

Additional co-authors are and Ryan Routsong in the 91探花civil and environmental engineering department, and Timothy Cary and Antonio Palazzo with the U.S. Army Cold Regions Research and Engineering Laboratory. This research was funded by the Strategic Environmental Research and Development Program and the Environmental Security Technology Certification Program of the U.S. Department of Defense.

For more information, contact Strand at sstrand@uw.edu.

Adapted from by the University of York.

We like to keep the air in our homes as clean as possible, and sometimes we use HEPA air filters to keep offending allergens and dust particles at bay.

But some hazardous compounds are too small to be trapped in these filters. Small molecules like , which is present in small amounts in chlorinated water, or , which is a component of gasoline, build up in our homes when we shower or boil water, or when we store cars or lawn mowers in attached garages. Both benzene and chloroform exposure have been linked to cancer.

Now researchers at the 91探花 have genetically modified a common houseplant 鈥� pothos ivy 鈥� to remove chloroform and benzene from the air around it. The modified plants express a protein, called 2E1, that transforms these compounds into molecules that the plants can then use to support their own growth. The team Dec. 19 in Environmental Science & Technology.

“People haven’t really been talking about these hazardous organic compounds in homes, and I think that’s because we couldn’t do anything about them,” said senior author , who is a research professor in the UW’s civil and environmental engineering department. “Now we’ve engineered houseplants to remove these pollutants for us.”

The team decided to use a protein called cytochrome P450 2E1, or 2E1 for short, which is present in all mammals, including humans. In our bodies, 2E1 turns benzene into a chemical called phenol and chloroform into carbon dioxide and chloride ions. But 2E1 is located in our livers and is turned on when we drink alcohol. So it’s not available to help us process pollutants in our air.

“We decided we should have this reaction occur outside of the body in a plant, an example of the ‘green liver’ concept,” Strand said. “And 2E1 can be beneficial for the plant, too. Plants use carbon dioxide and chloride ions to make their food, and they use phenol to help make components of their cell walls.”

The researchers made a synthetic version of the gene that serves as instructions for making the rabbit form of 2E1. Then they introduced it into pothos ivy so that each cell in the plant expressed the protein. Pothos ivy doesn’t flower in temperate climates so the genetically modified plants won’t be able to spread via pollen.

“This whole process took more than two years,” said lead author , who is a research scientist in the civil and environmental engineering department. “That is a long time, compared to other lab plants, which might only take a few months. But we wanted to do this in pothos because it’s a robust houseplant that grows well under all sort of conditions.”

The researchers then tested how well their modified plants could remove the pollutants from air compared to normal pothos ivy. They put both types of plants in glass tubes and then added either benzene or chloroform gas into each tube. Over 11 days, the team tracked how the concentration of each pollutant changed in each tube.

For the unmodified plants, the concentration of either gas didn’t change over time. But for the modified plants, the concentration of chloroform dropped by 82 percent after three days, and it was almost undetectable by day six. The concentration of benzene also decreased in the modified plant vials, but more slowly: By day eight, the benzene concentration had dropped by about 75 percent.

In order to detect these changes in pollutant levels, the researchers used much higher pollutant concentrations than are typically found in homes. But the team expects that the home levels would drop similarly, if not faster, over the same time frame.

Plants in the home would also need to be inside an enclosure with something to move air past their leaves, like a fan, Strand said.

“If you had a plant growing in the corner of a room, it will have some effect in that room,” he said. “But without air flow, it will take a long time for a molecule on the other end of the house to reach the plant.”

The team is currently working to increase the plants’ capabilities by adding a protein that can break down another hazardous molecule found in home air: formaldehyde, which is present in some wood products, such as laminate flooring and cabinets, and tobacco smoke.

“These are all stable compounds, so it’s really hard to get rid of them,” Strand said. “Without proteins to break down these molecules, we’d have to use high-energy processes to do it. It’s so much simpler and more sustainable to put these proteins all together in a houseplant.”

Civil and environmental engineering research technician Ryan Routsong is also a co-author. This research was funded by the National Science Foundation, Amazon Catalyst at 91探花and the National Institute of Environmental Health Sciences.

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For more information, contact Strand at sstrand@uw.edu or 206-543-5350.

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.

But those explosives and munitions leave behind toxic compounds that have contaminated millions of acres of U.S. military bases 鈥� with an estimated cleanup bill ranging .

In a published online Nov. 16 in , 91探花 and University of York researchers describe new transgenic grass species that can neutralize and eradicate 鈥� a that has been widely used in explosives since World War II.

91探花engineers 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.

鈥淭his is a sustainable and affordable way to remove and destroy pollutants on these training ranges,鈥� said senior author and 91探花professor of civil and environmental engineering , whose lab focuses on taking genes from microorganisms and animals that are able to degrade toxic compounds and engineering them into useful plants.

鈥淭he 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,鈥� Strand 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鈥檚 currently as a potential human carcinogen.

Unlike other toxic explosives constituents such as TNT 鈥� which binds to soils and tends to stay put 鈥� RDX dissolves easily in water and is more prone to spread contamination beyond the limits of a military range, manufacturing facility or battleground.

鈥淧articles get scattered around and then it rains,鈥� Strand said. 鈥淭hen 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 .鈥�

Wild grass species do remove RDX contamination from the soil when they suck water up through their roots, but they don鈥檛 significantly degrade it. So when the grasses die, the toxic chemical is re-introduced into the landscape.

Co-authors and , 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.

The bacteria themselves aren鈥檛 an ideal cleanup tool because they require other food sources that aren鈥檛 always present on military training ranges. So Bruce and Rylott tried inserting the bacterial genes into plant species commonly used in laboratory settings. Those experiments proved that the new plant strains were able to remove RDX contamination much more successfully than their wild counterparts.

鈥淐onsidering the worldwide scale of explosives contamination, plants are the only low cost, sustainable solution to cleaning up these polluted sites,鈥� said Bruce.

The 91探花team of civil and environmental engineers spent eight years working to express the same genes in plant species that could stand up to real-world use. They needed a hearty perennial species that grows back year after year and that has strong root systems that can bounce back after fires.

Grasses fit that bill, but they are more difficult to manipulate genetically. In particular, the 91探花engineers had to build into their gene constructs robust monocot 鈥減romoters鈥� 鈥� or regions of DNA that cause a particular gene to be expressed 鈥� for the process to work in grass species.

鈥淔or cleaning up contaminated soils, grasses work best, but they鈥檙e definitely not as easy to transform, especially since flexible systems to express multiple genes in grasses have not been used before,鈥� said first author and acting 91探花instructor .

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 91探花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.

鈥淚 think it would be ecologically acceptable because the genes we鈥檝e introduced degrade real pollutants in the environment and cause no harm,鈥� Strand said. 鈥淔rom my perspective, this is a useful technology that鈥檚 beneficial to the environment and has the potential to remove dangerous legacy contamination from decades of military activity.鈥�

The research was funded by U.S. Department of Defense. Co-authors include 91探花civil and environmental engineering research techs Ryan Routsong and Quyen Nguyen.

For more information, contact Strand at sstrand@uw.edu or 206-543-5350.

Grant numbers: SERDP ER-1498, ESTCP ER-201436