![]() This issue... Extremophiles Plant Information Superhighway Working Science: Glenn Seaborg Remembrance E-mail Reminder
This issue... Extremophiles Plant Information Superhighway |
ExtremophilesThe Ultramarathoners of the Microbe WorldBy James R. Weber To discover ways to remediate contaminated soils, researchers must sometimes go to considerable lengths--and depths. DOE national laboratory scientists are collaborating with university scientists from the U.S. and other countries to investigate microorganisms in the deeply buried rocks and groundwaters of the Witwatersrand Supergroup in South Africa. Toxic waste sites can poison or kill more commonly found organisms--those that require oxygen for survival. However, microbes that can live anaerobically (without oxygen) can tolerate the extreme conditions found in underground waste sites. Microbes that can withstand extremes of heat, cold, radiation, etc., generally called "extremophiles," are the ultramarathoners and endurance athletes of the microbe world. Such microbes might be useful in keeping contamination from spreading away from already contaminated radioactive and metal-saturated soil--an application that would be highly useful in many countries searching for ways to clean up contaminated soil. The research team, led by T.C. Onstott of Princeton University, went to the deep mines of the Transvaal region of South Africa looking for microbes that live at high temperatures and considerable pressures and that can handle an environment rich in uranium and organic carbon. Based on their knowledge of anaerobic microbes found elsewhere, researchers reckoned that deep mines could yield microbes that live in environments that are metal-rich and have a higher-than-average amount of radiation. In particular, they were looking for microbes inhabiting the "carbon leader," an organic-rich vein that is highly mineralized, containing high concentrations of uranium and pyrite and one of the richest gold deposits in the world. The carbon leader is believed to have originated from an intrusion of petroleum millions of years ago in deep regions of the earth. How deep? The research samples were collected from approximately 3.2 km (almost 2 miles) beneath the earth's surface, where the temperature of the rock is between 55° and 60°C (131° and 140°F). The carbon leader also contains low levels of radioactivity because of uranium. The very favorable conditions in the mines for extremophiles are emphatically not favorable for human beings. According to one researcher, the conditions deep in the mine were "as close to hell as I care to get." Miners can go down to 5 km (over 3 miles) when the price of gold warrants it. However, recent cheap gold means that shafts are used "only" as deep as about 3.5 km (2.2 miles). The shaft and stopes (the side-shafts where the mining is actually done) are confined and very hot--around 60°C (140°F). Jim Fredrickson of the Pacific Northwest National Laboratory remembers that mining-induced earthquakes rock the shafts and the surface several times a day--"It could be very disconcerting when you're in the mine, especially in the stopes." The daunting conditions underground are almost matched by the challenges in handling the samples once they were retrieved. Sampling has to be done using aseptic techniques to prevent potential contamination from microbes on the equipment and research staff's clothing. Rock samples were processed at the mine to remove the outer, potentially contaminated surfaces. Crushed rock fragments and groundwater collected from boreholes in the stopes were used to inoculate the growth media in the sampling containers before the samples were added. The team also collected samples that may tell stories about chemical and biological processes that occur around the microbes themselves--nucleic acids and membrane lipids, for instance, that may tell about how the microorganisms metabolize and live and who they are. Although it's still early in the analysis, preliminary results from the samples have been encouraging. For instance, a newly discovered form of the bacterium Thermus sp. was isolated from a groundwater sample. This microbe is moderately radiation-resistant, grows anaerobically, and in the mine environment interacts with forms of iron, chromium, cobalt, and uranium, forms of elements that may be found in contaminated soils. Although the physiology and genetics of the microbe have been studied for nearly three decades, no other form previously studied has shown this metabolic versatility. This research is supported by SC's Natural and Accelerated Bioremediation Research (NABIR) Program. Funding is also jointly sponsored by the National Science Foundation's Life in Extreme Environments (LExEn) Program through a grant to Princeton University. Additional partial support for some scientists traveling to South Africa was provided by the National Geographic Society. Contact T.C. Onstott, Department of Geosciences, Princeton University, tullis@princeton.edu. For more information, see Princeton's Geomicrobiology Research Group's website * Reference: Bioremediation of Metals and Radionuclides: What It Is and How It Works, A NABIR Primer, "Section IV: A Look at Microbial Metabolism," pp. 34-35. http://www.lbl.gov/NABIR/primer/primer.html | ![]() ![]() ![]() ![]() ![]() |
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