Green Genes:
Genetic Technologies for the Environment

Gene technologies are spreading at ORNL. They are being used to improve the usefulness of microorganisms and green plants.

Detecting land mines using microbes.
Reengineered bacteria could save people from underground devices engineered to kill them. These devices are land mines, which kill or maim 25,000 people a year. They are extremely difficult to find once they are buried in the ground. Plastic mines are almost impossible to locate because they elude metal detectors. Fortunately, most land mines leak slightly and leave traces of explosive chemicals such as TNT shortly after they are installed. ORNL has developed a clever way of using bacteria to detect this faint explosive signature.

Mike Maston and Billy Schaefer
Mike Maston (left) and Billy Schaefer examine an area around a land mine, taking soil samples from a site that was identified as a mine using the ORNL Microbial Mine Detection System. The insets show a tube of the microorganism as it fluoresces and a typical antipersonnel mine.
Bob Burlage, a microbiologist in ORNL's Environmental Sciences Division, has genetically engineered microorganisms to emit light in the presence of TNT. As they recognize and consume TNT, the engineered bacteria produce a fluorescent protein that appears as a green light when they are illuminated by ultraviolet (UV) light.

"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 says. "We attached a green fluorescent protein gene obtained from jellyfish to these activated genes and included a regulatory gene that recognizes TNT. As a result, the attached gene will also be turned on. It will produce the green fluorescent protein, which emits extremely bright fluorescence when exposed to UV light."

In a field demonstration in October 1998 in South Carolina, Burlage and his ORNL colleagues Martin Hunt, Steve Hicks, Mike Maston, Mike Keleher, and Keith Williams (all of the Instrumentation and Controls Division) successfully used the microbial technique to detect five out of five simulated mine targets in a 300-square-meter field. "In less than a year," Burlage says, "we went from the lab bench to the field and got better results than we expected. Microbial mine detection is much closer to commercialization than we anticipated."

The technique offers several advantages. It is inexpensive. It poses no hazard to operators. And it is virtually the only mine detection technology that could be used in the near future to detect mines over a very wide area. Now that Burlage has shown a better way to find land mines, he is hoping for support to move the technology into the commercial sector to help save lives.

Genetics and biomass energy.
Genetic research has played an important role in DOE's Bioenergy Feedstock Development Program since its inception 20 years ago at ORNL. The purpose of the program is to develop renewable, biomass resources (e.g., poplar trees and switchgrass) that can be converted to liquid transportation fuels and chemicals or burned to produce electricity.

Heat-pulse probes inserted in cottonwood tree
This series of heat-pulse probes inserted at various depths in a cottonwood tree provide measurements to help ORNL scientists estimate whole-tree water use in an experiment examining the interactions between genetics and environment in determining plant growth and productivity. This research is part of a CRADA project with Union Camp Corporation.
Program researchers at ORNL and elsewhere have identified model energy crop species for major U.S. agricultural production regions. Using molecular genetics and other breeding techniques, they have developed highly productive poplar varieties now being used for paper production. They have produced the first genetic linkage map for a hardwood tree species. They are exploring genetic marker–aided selection to tailor energy crops to maximize the energy they will produce.

At ORNL the program is led by Janet Cushman and Lynn Wright. Participating ORNL researchers are Anne Ehrenshaft, Mark Downing, Sandy McLaughlin, Marie Walsh, Virginia Tolbert, and Jerry Tuskan. Tuskan recently helped identify the first genetic marker limited to sex determination in trees. He used hybrid willow trees, which grow fast and are a good fuel source. The marker is present in all female hybrid willow trees but absent in the male trees. Early gender identification is important because male hybrid willow trees are more resistant to drought than female willows. Thus, the male trees are potentially more desirable for bioenergy plantations during global warming.

The Bioenergy Feedstock Development Program, Cushman says, will continue to use genetic technologies to make bioenergy resources less expensive and more competitive with fossil fuels. The appeals of bioenergy resources are that they are produced domestically, they offer a potential new market for farmers, and their consumption will not boost carbon dioxide levels in the atmosphere, slowing the onset of potentially devastating climate change.


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