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Benzene Busters

Microorganism discovery could pave way for removing toxic chemical from the environment

MONDAY, Dec. 24, 2001 (HealthDayNews) -- Scientists have identified two microorganisms that may provide an effective way to remove benzene, a highly toxic chemical, from the environment, a recent study says.

The organisms, known as Dechloromonas strains RCB and JJ, can "biodegrade" benzene to carbon dioxide without the help of oxygen. That ability could be crucial in cleaning contaminated soil and groundwater.

Scientists have spent 20 years looking for an organism capable of this kind of action, says lead researcher John D. Coates, an assistant microbiology professor at Southern Illinois University.

Benzene is a major component of gasoline and other petroleum-based fuels and also is used as a solvent in many chemical manufacturing processes, including paint production. Long-term exposure to benzene can lead to cancer in humans.

While benzene biodegrades quickly when exposed to air, it's much more difficult to remove from places where there is a lack of oxygen.

Fuel spills and leaking underground storage tanks at gas stations are major causes of benzene pollution. When there is a spill or leak, oxygen-dependent bacteria start to break down the gasoline.

"The activity of those organisms will deplete the environment of oxygen very rapidly. So the environment becomes anaerobic. At that stage, what normally happens is gasoline degradation comes to a standstill," Coates says.

"So what happens at that point is the more soluble components like benzene and toluene start moving out into the groundwater and move toward drinking water supplies. As a result, you can get contamination of drinking water from benzene," he adds.

But the lack of oxygen is no problem for the Dechloromonas strains RCB and JJ, which are common in many soils.

"You can either add these organisms to the groundwater," Coates says, "or you can test the groundwater to see if these organisms are already present there as indigenous bacteria and stimulate their growth" by providing them with nitrate.

Although he and his team have done extensive lab research, their next step is a field trial. They're looking for industrial partners to test bioremediation using the two microorganisms.

Coates and his team also are doing more lab work to determine whether these microorganisms can degrade other chemicals in gasoline.

The potential benefits of this research extend beyond cleaning up gasoline spills and leaks.

"From an academic standpoint, this is of great interest because it will help us identify the pathway by which the organism actually degrades stable carbon structures like benzene," Coates says. "Now that we have the organism in hand, we can start looking at the pathway and the enzymes involved."

A better understanding of those pathways and enzymes could have future biotechnology applications.

Scientists have known for some time that something in the soil is able to break down benzene in anaerobic conditions -- they just haven't been able to pinpoint the microorganisms that do it.

Brian Fox, an associate biochemistry professor at the University of Wisconsin-Madison, calls Coates' work an "important discovery."

"I think it's always an important discovery to have a pure organism that does something like this, because now you can really begin to sort out what are the exact details of the process," Fox says.

And he adds: "Not to be facetious or anything, but it's like finding the Abominable Snowman or some other unknown creature that's suspected to be there but has not been really found yet."

The results of Coates' research were published in a recent issue of the journal Nature.

What to Do: For more information on using bacteria for bioremediation, check out Bugs that Scrub from the University of Wisconsin-Madison, or go to the U.S. Geological Survey.

SOURCES: Interviews with John D. Coates, Ph.D., assistant professor of microbiology, Southern Illinois University, Carbondale; Brian Fox, Ph.D., associate professor of biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison
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