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[QUOTE]Originally posted by Dustoff101: [QB] Wanted: Bugs That Scrub Harnessing bacteria for environmental cleanup This sample of groundwater from contaminated soil could yield bacteria that can degrade persistent soil pollutants. The United States is investing billions of dollars to clean up polluted groundwater and soils. In Wisconsin alone, the Department of Natural Resources has a list of nearly 10,000 sites that need to be cleaned up. In 1998, contaminants turned up in well water samples from Beloit to Rhinelander. Some communities removed individual wells from service because water from those wells contained pollutants considered unsafe for drinking. The most common soil and groundwater pollutants include fuels such as gasoline and oil, industrial compounds such as TCE (trichloroethylene) and PCBs (polychlorinated biphenyls) and pesticides. Many of the compounds are threats to human health. Exposure to benzene or TCE, for example, is known to increase the risk of cancer. What's wrong with the "pump and treat" approach? Efforts to clean up these toxins have cost far more than anticipated and the results have been discouraging. Conventional methods bring contaminated soil and water to the surface before treating it. Such "pump-and-treat" methods may continue for decades at a polluted site and basically transfer the contaminants to the air or to landfills. As the limitations of these methods become clearer, experts have become more interested in biological remediation. Bioremediation relies on microbes to destroy hazardous contaminants in place by transforming them into less harmful compounds. The transformation occurs naturally at contaminated sites and has controlled the spread of some pollution without pump-and-treat methods. Those who advocate an expanded role for bioremediation say it will be less costly, faster and safer than pump-and-treat methods, and can be combined with them. Bacteria: Doing what comes naturally Bacteria are the key players in bioremediation, which builds on the role they have played in nature for billions of years. These microscopic organisms live virtually everywhere. They break down complex plant, animal and human waste. Bacteria chew up any compound that provides the energy or nutrients they need, even if it's a relatively new compound to them. Looking for contaminant-eating bacteria that can exist without oxygen. Graduate student Michele Zwolinski uses an oxygen-free chamber to work with samples from the Fort McCoy site. She is trying to isolate bacteria that can degrade groundwater contaminants in the absence of oxygen. "Wherever contaminants are present there's strong selection for bacteria that can get some energy from the compounds," says biochemist Brian Fox. "The pollutants that accumulate in the environment are those that aren't a food source for bacteria or that produce toxins when bacteria metabolize them. Or maybe some bacteria can degrade these compounds, but just do it very slowly. "If such bacteria do exist, perhaps we can improve their ability," Fox says. "What we're trying to do is to speed the process of breakdown." Fox is one of three CALS scientists trying to harness the power of bacteria to enhance the cleanup of environmental pollution. He studies a bacterial enzyme that can break down some of our most troublesome groundwater contaminants -- benzene, dichloromethane, trichloroethylene and similar pollutants. To learn how the enzyme works, Fox has been making changes in the gene that produces it. The genetic changes alter the enzyme's structure. Fox can then see how the alteration affects its ability to degrade different compounds. Bioremediation has become a fast-growing sector of the hazardous waste cleanup industry. Fox collaborates with scientists at Envirogen, Inc., a New Jersey-based company, that is evaluating the altered enzymes Fox produces to see if they can attack contaminants. Bacteria face off with a gas spill Soil scientist Bill Hickey is examining what happens in a diverse microbial community when bacteria there come face to face with a gasoline spill. Hickey and hydrogeologist Jean Bahr, from the College of Letters and Science, are studying a fuel spill at Fort McCoy, near Sparta. Bahr is documenting how the plume of contaminated water moves. Hickey, a soil microbiologist, is isolating bacteria that degrade hydrocarbons in groundwater that has no oxygen. Hickey has studied ground contaminated by leaking fuel tanks and was the first to show that bacteria could degrade TCE in water year-round under Wisconsin conditions if he supplied the bugs with ammonium as a nitrogen source. Now he's looking for bacteria that can degrade benzene. Benzene is a relatively minor component of gasoline, but it's the most toxic component to people and one that bacteria degrade slowly. "Hydrocarbons are a rich carbon source and bacteria immediately attack them when hydrocarbons enter groundwater," Hickey says. "The intense bacterial activity rapidly uses up what little oxygen was present in the groundwater. When oxygen disappears from groundwater many bacteria can no longer survive there, and that slows down the cleanup." Wanted: Microbes that exist where oxygen doesn't Hickey wants to identify bacteria that degrade benzene and closely related compounds in the absence of oxygen. In the laboratory, he is testing the microbial community from uncontaminated groundwater at Fort McCoy to see how that community changes when he adds hydrocarbons. He has found a major shift in the bacteria present when he adds benzene. Hickey has already isolated bacteria that can degrade hydrocarbons similar to benzene in water devoid of oxygen. Now he hopes to find species that can degrade benzene itself. Microbial physiologist Glenn Chambliss and his colleagues have identified two bacteria and the enzymes that enable them to degrade nitroglycerin and TNT. "This is the first time anyone has purified and characterized enzymes that can take the initial step in breaking down TNT," says Chambliss, who chairs the Department of Bacteriology. The findings may lead to biologically based methods for cleaning up soils contaminated with toxic residues left from manufacturing explosives, according to Chambliss. There are an estimated 10,000 U.S. sites contaminated with explosives and related compounds. The materials include: TNT (trinitrotoluene), DNT (dinitrotoluene), nitroglycerin, and nitrocellulose, also known as smokeless gunpowder. TNT and DNT are particularly toxic and break down very slowly. Wanted: Bacteria that eat dynamite To find bacteria that could "eat" dynamite, Chambliss and his colleagues collected bacteria from sites once contaminated with nitroglycerin at the Badger Army Ammunition Plant near Baraboo. The plant was once the world's largest producer of smokeless gun powder, a propellant used to fire artillery shells. The researchers identified several bacteria that could survive at high nitroglycerin concentrations and degrade the compound. They have sequenced the genes that code for different enzymes from two species. One enzyme is five times as efficient as the other at degrading TNT. The more efficient enzyme can follow two different pathways in degrading TNT, according to Chambliss. "One leads to toxic components that don't decay further. The other pathway leads to a partial but more complete breakdown without toxic compounds." Chambliss is now experimenting to see if he can engineer the enzyme so it only works via the preferred pathway. He, Brian Fox and environmental engineer Dan Noguera from the College of Engineering are also looking for other bacteria and enzymes that will complete the cleanup. Cleaning up pollutants can be like running an assembly line in reverse. You start with a complex molecule and the bacteria break it apart, eventually reducing it to water and carbon dioxide. It takes bacterial teamwork "Bacteria like those that work on TNT often move the degradation process only a certain distance before producing a compound they can no longer benefit from or that is too toxic to keep around," says Fox. "They put that compound back into the environment where other bacteria will hopefully degrade it further. The chain may take several steps before it produces harmless compounds." Chambliss and Fox hope to find what Fox sometimes calls the "missing link," one bacterium or several that will take the partly degraded TNT molecule and reduce it to compounds that known bacteria can fully degrade to carbon dioxide and water. You can try to create these bugs or look for them in nature, Fox says. If bacteria can break down a compound, he feels certain that researchers have the best chance of finding those bacteria in nature. "Nature is the greatest experimenter of them all. Nature's experiments go on 24 hours a day, 365 days a year," he says. From lab tests to commercial applications: A long leap "It's a major leap from academic research to companies implementing these findings," says Hickey. But the three College scientists know the contaminants are likely to be a problem for a long time to come. "The bugs have the potential to address these contamination problems," Chambliss says. "But we're still at an early stage in understanding the processes involved. It took us a long time and a great deal of research to develop an industry around the antibiotics that bacteria produce. It's going to take more research before we get bacteria that can solve some of these environ- mental problems." [/QB][/QUOTE]
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