The University of Tennessee's Center for Environmental Biotechnology (CEB), in collaboration with Oak Ridge National Laboratory (ORNL) and the U.S. Environmental Protection Agency, released an organism in 1996 known as Pseudomonas fluorescens HK44. The organism, which specifically targets naphthalene one of several polycyclic aromatic hydrocarbons (PAHs) present at DOE sites around the country represents an existing organism that has been genetically altered to produce light as it degrades a specific contaminant.

The organisms were released into six steel-lined tanks on the Oak Ridge Reservation. These tanks, or soil lysimeters, measure 8 feet in diameter and 10 feet deep. The circular cluster of lysimeters has an 18-foot-deep central core area from which researchers monitored the progress of the organisms as they degraded contaminants in the soil.

As the organisms degraded the naphthalene, they emitted light. Bundles of fiber-optic cables snaked from various points within the lysimeters to photomultipliers, which amplified the light and digitalized it for analysis by researchers. The lysimeters were also equipped with other devices to monitor moisture, soil pH, temperature, and the presence of carbon dioxide and oxygen, which reflect the microorganisms' metabolic activity.

Naphthalene and other PAHs, which are derived from fossil fuels, are widely distributed in the environment and are regarded as potential carcinogens. The project allowed researchers at that time to study which environmental conditions could influence the ability of microorganisms to degrade soil contaminants.

"Our primary expectation from this project was to understand how we could actually control microbial processes in the environment to achieve maximum levels of degradation," says CEB Director Gary Sayler, who served as co-principal investigator on the project. According to Sayler, the GEMs performed exactly as expected in detecting and degrading the naphthalene.

One surprise, however, involved the level of organism die-off, says Robert Burlage, an ORNL microbiologist and one of the principal investigators on the project. According to Burlage, the GEMs at times reached such low levels that there was no visible light, primarily because most of the hydrocarbon pollutants had been degraded by that time. However, in that low state, it took only a little oxygen to keep them alive.

Now, Sayler says, there seems to be more interest in using the GEMs in "sentinel detection" than for bioremediation. Sentinel or first-alert detection of specific substances presents a variety of uses for the GEMs. One area of current research involves the use of GEMs in the detection of hazardous substances in space environments. This use also has potential application in monitoring ailments related to "sick-building" syndrome. Please see "War of the Microbes," "Critters in Space," and "Fluid Ounces" Spotlights.

For more information contact:

Gary Sayler
CEB, The University of Tennessee
676 Dabney Hall
Knoxville, TN
37996-1605

or call: 865-974-8080