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Fiber Optic Research Glowing with Promise for the Environment

by Alicia P. Gregory

When most people think about fiber optics, they think of telephone or cable service and visualize a bundle of glass or plastic threads that transmit data at close to the speed of light. One University of Kentucky researcher is taking fiber optics beyond communications to produce highly sensitive environmental monitoring tools.

Since 1995, Sylvia Daunert, an associate professor of chemistry, has been working on an NSF-funded project to produce fiber optic sensors that use bacteria genetically engineered to glow in the presence of very low-but still dangerous-levels of toxic substances. This bioluminescence is created by altering the same proteins that make fireflies and jellyfish glow.

Daunert, originally from Barcelona, Spain, has a joint appointment in the Department of Pharmaceutical Sciences in the College of Pharmacy, and is a faculty associate of the Center of Membrane Sciences. In this fiber optic project, she is studying the toxic substances arsenic and antimony, a chemical used in matches. Daunert's lab is also involved in ongoing studies of copper, PCBs and sugars.

Photo of Sylvia DaunertSylvia Daunert is producing fiber optic sensors that glow in the dark, like fireflies and jellyfish.

"We've moved beyond luciferase, the protein that makes the firefly emit light, to a little bit more sophisticated system by using different proteins that can emit different colors," Daunert says. "This is very exciting because now we can detect many toxic substances at the same time just by looking at which color-red, green or blue-is emitted. We are tapping into the selectivity that nature offers us with these proteins."

The bacteria Daunert and her colleagues use is a non-toxic strain of E. coli, a very common bacteria widely used in biotechnology.

Daunert creates her bioluminescent bacteria by using natural bacterial genes that recognize small amounts of toxic substances. "What we do is kind of trick the bacteria by hooking up the gene that recognizes a toxic compound to what we call the reporter gene-the one that generates the bioluminescent signal," she says. "So as the toxic compound enters the cell, it is being recognized by the gene which triggers the production of the reporter."

Daunert attaches these bacteria to the optic fibers by trapping them in solution behind a membrane. "The membrane has pores that only allow small molecules to pass through, so the bacteria are trapped; but compounds like arsenic or sugars can pass through," she says.

The advantage of using these optic fibers for environmental monitoring lies in their ability to act as remote sensors. "You can place a fiber at a polluted site, say an industrial river that you want to monitor in a continuous manner. You can just leave the fiber there and monitor what is happening from miles away," says Daunert. Although she has not yet explored the logistics of how this will work, Daunert points to the ease with which signals pass through fiber optic wires across telephone poles or underground. It may soon be possible for a farmer to monitor his water supply by checking a graph of the sensor output sent directly to his computer.

Daunert says such a process will be highly effective and feasible. There is currently no method to detect the low levels of toxic substances Daunert's engineered bacteria are designed to detect. "Our method is a billion times more selective for arsenic and antimonite than current tests. It separates other compounds that are structurally related, so you have very little interference from anything else that is present in the sample," she says.

"We are also moving in the direction of freeze-dried bacteria, bacteria you can take to the field in a little pouch and reconstitute with solution on the spot to do your test," Daunert says. "Although we haven't done a market study, using our technology should be pretty cheap. Bacteria are very cheap and the instrumentation you need is not elaborate. A sensitive, hand-held luminometer that measures the light emitted by our sensors costs less than $5,000.

"The most significant thing I think we have done in the past four years is to demonstrate that we can use this technology to detect many different substances, even several different substances at once," Daunert says.

In September 1998, her work on reporter genes and bioluminescence was featured as the cover-story of Analytical Chemistry, the most important journal in her field. Daunert's research at UK has been supported by federal institutions including the National Science Foundation (a CAREER Award), the Department of Energy, the National Aeronautics and Space Administration, the Department of Defense, and the National Institutes of Environmental Health. In 1996, she was selected as a Cottrell Scholar and was awarded $50,000 by the Research Corporation, a foundation for science and technology advancement. In 1997 she won the $10,000 Lilly Faculty Award in Analytical Chemistry. Eli Lilly renewed this award for a second year in 1998.