Researchers develop microbes and plants to detect explosives in soil

To detect toxic explosive residues in the soil – including unexploded artillery shells and other weapons – Florida researchers are using genetic engineering to modify microbes and plants that can be used as “biosensors.” The three-year research project, supported by a $2.3 million contract from the U.S. Department of Defense’s Advanced Research Projects Agency, will help clean up thousands of acres of land that have been used for military training in the United States and abroad.

From the University of Florida:
UF RESEARCHERS DEVELOPING MICROBES AND PLANTS TO DETECT EXPLOSIVE COMPOUNDS IN SOILS

Feb. 6, 2003
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GAINESVILLE, Fla. — To detect toxic explosive residues in the soil – including unexploded artillery shells and other weapons – University of Florida researchers are using genetic engineering to modify microbes and plants that can be used as “biosensors.”

The three-year research project, supported by a $2.3 million contract from the U.S. Department of Defense’s Advanced Research Projects Agency, will help clean up thousands of acres of land that have been used for military training in the United States and abroad.

“Many of these areas are far too vast for current remediation technologies, and new methods must be found to accurately identify localized areas of contamination for a more focused cleanup effort,” said Lonnie Ingram, a professor of microbiology and cell science with UF’s Institute of Food and Agricultural Sciences. He leads a five-member faculty team working on the defense contract.

“Most of these military training areas are contaminated with toxic explosive residues and unexploded ordnance,” Ingram said. “Before they can be cleaned up and returned to public use, methods must be developed to map or identify the problem areas for cleaning.”

Of equal importance, he said, the research will identify clean regions that do not contain explosive residues or materials. Clearly identifying areas that pose no danger to people, plants or the environment will greatly reduce costs.

Ingram said different microbial and plant biosensors also could be developed for use in monitoring other types of environmental pollution, such as pesticide or chemical contamination.

The goal is to develop microbes and plants that can be used as sensitive biosensors for the presence of explosive compounds such as TNT and their breakdown products in the soil.

“Bacteria and plants will be genetically engineered to produce visible responses to the presence of TNT and their degradation products in the soil,” Ingram said.

“For example, we are developing sentinel bacteria that can be sprayed on contaminated sites and will produce fluorescent pigments – painting the soil surface with colors that show the presence of explosive chemicals,” he said. “Contaminated areas could then be mapped and quantified by aerial surveillance or satellite.”

Similarly, the UF team will genetically modify plants so they will change in pigmentation as a response to soil contamination. The response system in plants will incorporate sensors initially developed in bacteria.

“Unlike bacteria that respond primarily to surface contamination, plant roots penetrating the soil should provide a more-sensitive measure of buried materials,” Ingram said. “Together, the sentinel bacteria and plant systems should provide effective new tools to help remediate military lands.”

Bill Gurley, a professor in UF’s microbiology and cell science department also involved in the project, said the strategy of adapting bacterial sensing systems for functions in plants offers several advantages.

“First, the simplicity of the bacterial system, where only two or three proteins are involved in signal recognition and gene activation, will make transfer and adaptation to plants easier,” he said. “Second, conducting the initial genetic development in bacteria should enable us to obtain a larger number of mutants for TNT recognition prior to transfer into plants.”

Gurley said organisms often perceive signals from their surroundings in the form of energy or chemical gradients. Plants now can sense light, gravity, heat, hormones and soil compounds. Bacteria have an extensive array of sensors for chemicals in their environment.

“We hope to expand plant perception by engineering new pathways of signal recognition derived from bacterial sensors that have been modified to recognize a variety of compounds of interest,” he said.

“Upon recognition of a chemical signal, the plant could be engineered to respond by changing its pigmentation, or perhaps, by switching on or off a cellular processes such as flowering,” Gurley said. “In a sense, this is the beginning of two-way communication between plants and man.”

Other faculty working on the project include Nemat Keyhani and Thomas Bobik, assistant professors in UF’s microbiology and cell science department, and Shouguang Jin, an associate professor of molecular genetics and microbiology at the UF College of Medicine.

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