Illuminating Landmines: Genetically engineered bacteria glow a soft green when they digest trinitrotoluene (TNT), a commonly used explosive. When illuminated by ultraviolet light, the fluorescent glow is clearly visible at night. "Land mines leak small amounts of TNT over time, leaving a chemical trace for bacteria on the soil surface," Robert Burlage of Oak Ridge National Laboratory says. "When the bacteria of one of our strains of Pseudomonas putida encounter the TNT, they will scavenge the compound as a food source, activating the genes that produce proteins needed to digest the TNT." Burlage and his coworkers at ORNL team attached the green fluorescent protein (GFP) gene to the genes that are expressed (activated) only during TNT digestion. GFP, which is derived from jellyfish, emits extremely bright fluorescence when exposed to ultraviolet light.
Burlage and his team successfully field-tested the bacteria in preliminary trials at the National Explosives Waste Technology and Evaluation Center in Edgefield, South Carolina. The technology holds great promise for immediate, reliable, and inexpensive detection because the bacteria can be produced in bulk, and the application process -- manual or aerial spraying -- is simple and economical. Experts estimate there are approximately 100 million mines in former combat zones in more than 60 nations. Mine fields in countries such as Bosnia, Cambodia, and Kuwait annually kill or maim an estimated 26,000 people, and prevent development of natural resources and land that could be used for agriculture and industry. Initial research into this area was supported by SC's Office of Biological and Environmental Research. The project is now sponsored by the Defense Threat Reduction Agency (http://www.dtra.mil) within the Department of Defense.
Contact: Robert Burlage, ORNL, burlagers@ornl.gov