Scientists Discover First Ever Single-Species Ecosystem

Scientists have uncovered life in a South African gold mine, 2.8 kilometers (1.7 miles) beneath the surface of the earth. In this dark but hot ecosystem, a single biological species derives power not from the sun but from elements produced by uranium’s radioactive decay.

Remarkably, it is the first ecosystem ever found having only one biological species. In utter darkness, total isolation, with no oxygen, and in 60-degree-Celsius heat (140 degrees Fahrenheit), the cave-dwelling, rod-shaped bacterium, Desulforudis audaxviator survives.

Trajectories of evolution have fitted the bacterium with the genes necessary to exist under a variety of different conditions. One such adaptation is the ability to survive by fixing nitrogen and carbon directly from the environment.

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It shares most of these typical genes with archaea, members of a separate domain of life with no relation to bacteria, according to a report published in the 10 October, 2008 issue of the journal Science.

Researchers from US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), Joint Genome Institute (JGI), and Pacific Northwest National Laboratory (PNNL), as well as others from a range of universities including MIT and Princeton made the discovery in a project run by the Virtual Institute for Microbial Stress and Survival (VIMSS).

Although a single species ecosystem is a first for science, researchers aren’t surprised that the species is D. audaxviator. This microbe was first discovered in 2006 and is the most common microbe living below 1.5 km underground in this region of South Africa. Because the bacterium lives alone, it must build its organic molecules by itself out of water, inorganic carbon, and nitrogen from ammonia in the surrounding rocks and fluid.

Explaining the organism’s long journey to the extreme depths, the scientists suggested the bacterium hasn’t been exposed to pure oxygen for a very long time, perhaps millions of years.

Source: Lawrence Berkeley National Laboratory

Image credit: Micrograph by Greg Wanger, J. Craig Venter Institute, and Gordon Southam, University of Western Ontario, used with permission.

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