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Methane-producing microbes dominate in hot spring


Scientists have identified a highly unusual community of methane-producing microbes in a hot spring 200 meters below ground in Idaho. The community may offer clues as to how life forms elsewhere in the universe survive in apparently hostile environments.

The microbes are able to live in such extreme conditions, researchers say, because they generate energy by combining carbon dioxide with hydrogen from rocks in the geothermal spring. This chemical process produces methane, and the microbes are called methanogens. They are members of the archaea family, an ancient branch of life distinct from plants, animals, and bacteria.

Methanogens thrive in extreme environments such as geothermal springs.

Francis H. Chapelle, of the US Geological Survey in Columbia, South Carolina, and colleagues analyzed DNA sequences recovered from the waters of Lidy Hot Springs in Idaho and found that more than 90 percent of the organisms were methanogens. This is the highest-known concentration of such microbes discovered so far in any one place.

"These results demonstrate that hydrogen-based methanogenic communities do occur in Earth's subsurface, providing an analogue for possible subsurface microbial ecosystems on other planets," Chapelle and colleagues write in Nature.

The researchers collected the samples by boring a hole that tapped into the spring in a deep fracture zone about 200 meters underground. They isolated and sequenced DNA from the hot spring for phylogenic analysis. All but three of the 65 archaeal sequences appeared to be from methanogenic microbes.

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Chapelle, F. et al. A hydrogen-based subsurface microbial community dominated by methanogens. Nature 415, 312-315 (January 17, 2002).

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