Winter 2003

COVER STORY – "SIGNALS in the SEA" The Broad Side You Are What You Eat Where's That Smell? Hot on the Trail Avoiding Costly Mistakes Key Ingredient A Gut Feeling

A Gut Feeling Microbiologist examines fish guts to learn if he can exploit chemical signaling for environmental cleanup.

FRANK LOEFFLER wants to take advantage of microorganisms.

photo by Gary Meek Assistant Professor Frank Loeffler, a microbiologist, and postdoctoral fellow Kirsti Ritalahti want to exploit the natural chemical communication processes of marine organisms, including microorganisms, to clean up sites contaminated with chlorinated compounds. (300-dpi JPEG version - 619k)

Loeffler, a microbiologist and assistant professor of environmental engineering at Georgia Tech, believes he can exploit the natural chemical communication processes of marine organisms, including microorganisms, to clean up sites contaminated with chlorinated compounds.

"We need to understand how organisms work and then implement an engineering solution using what we know from microbiology," Loeffler says. Engineers sometimes introduce microorganisms to degrade contaminants at a polluted site or stimulate microorganisms that are already present there to do the job. Such strategies are called bioremediation.

Finding the right microorganisms to make these strategies work is challenging, but promising, in marine environments. Many higher aquatic organisms communicate with chemical signals that are actually chlorinated compounds produced by the organisms to perform some basic function, such as predator protection, Loeffler explains. For example, a species of algae produces a chlorinated compound that deters some species of fish from eating it.

"We want to take advantage of these signaling processes," Loeffler says. "So we are studying the guts of fish to see what microorganisms are present and are being used to break down chlorinated compounds. Then we can exploit the microorganisms for use in various polluted environments.... Some fish won't eat a certain plant because the plant is protecting itself by producing chemicals that don't taste good. But other fish actually eat toxic compounds. The microorganisms we are finding in them are most promising for bioremediation applications."

courtesy of Frank Loeffler Professor Loeffler and his colleagues have identified a new species of chlorine-eating microbe in the guts of parrotfish collected off the coast of Florida last year. (300-dpi JPEG version - 619k)

There is no shortage of naturally produced chlorinated chemicals in marine environments, especially in warmer climates, Loeffler adds. In a study that began in August 2002, Loeffler collected two types of fish off the coast of south Florida. One species eats algae containing a chlorinated compound, and the other does not.

"We are looking at the microbes in the intestines of these fish," Loeffler says. "What can they do? What we find may lead to new discoveries."

Researchers are identifying the chlorinated chemicals they believe the fish consume in their diet. Then in the lab, they can selectively enrich for the microbes that break down the chlorinated compound in the fish's gut. The ultimate result is a single population of the target microorganism. Research can then focus on how to use that organism for bioremediation.

Loeffler hopes his research will help change the environmental engineering profession's approach to bioremediation.

courtesy of NOAA Researchers are examining the guts of parrotfish to identify the chlorinated chemicals they believe the fish consume in their diet. Then in the lab, they can selectively enrich for the microbes that break down the chlorinated compound in the fish's gut. The ultimate result is a single population of the target microorganism. Research can then focus on how to use that organism for bioremediation.

Now, engineers typically take samples from a contaminated site to see what microorganisms are present and which ones might be exploited for clean up. But Loeffler suggests that bioremediation efforts should begin with research on natural environments where microorganisms are often abundant and have had time to genetically adapt to naturally occurring, low levels of chlorinated chemicals.

"In an evolutionary timeframe, 10 to 20 years of contaminant exposure is not enough time to develop the biological machinery to degrade chemicals efficiently at polluted sites," Loeffler says. "But a natural environment is a good place to find the source of the genetic information – the organisms degrading lower concentrations of contaminants. These organisms have had time to specialize to take advantage of this chemistry."

It is still an open question whether such microorganisms can degrade higher concentrations of contaminants, Loeffler adds. "Often, that's a limiting factor for degradation. But we may be able to manipulate the system to enhance their capabilities. We are looking for clues about how they degrade the chemicals."

In the process, researchers such as Loeffler want to know the ecological effects of introducing organisms to clean up contaminants. He and others are using nucleic-acid-based tools to monitor communities and quantify microorganism populations that are degrading the toxic chemicals.

"In my experience, the organisms have had no negative impact on the environment," Loeffler says. Overall, the community structure returns to its natural state following the bioremediation treatment, according to Kirsti Ritalahti, a postdoctoral researcher in Loeffler's group.

– Jane M. Sanders

For more information, contact Frank Loeffler, School of Civil and Environmental Engineering, Georgia Tech, Atlanta, GA 30332-0512. (Telephone: 404-894-0279) (E-mail: frank.loeffler@ce.gatech.edu)

Back to the Top

Contents    Research Horizons    GT Research News    GTRI    Georgia Tech

Send questions and comments regarding these pages to webadmin@edi.gatech.edu
Last updated: April 12, 2003