Almost two miles beneath the earth's surface in a South African goldmine, researchers have found a new species of bacteria that lives in total isolation from any other organism. The discovery offers the first known example of an ecosystem that isn't a complex web of different life forms, but is instead hosts just one self-sufficient species. The bacteria, Desulforudis audaxviator, is able to extract all its food and energy directly from the surrounding water and rocks, and researchers say the independent microbe offers a glimpse of the shape life could take on other planets. Researchers wanted to know what organisms were living in the mine's deep fissures, a habitat completely devoid of light and oxygen, so they analyzed the genes present in a water sample to determine what species lived there.

They filtered a total of 5,600 liters of mine water to get their sample, which gave other microbes plenty of opportunities to make themselves known. Of the DNA sequences obtained from this sample, over 99.9 percent were from this single species; over half of the remainder were obvious contaminants from their own lab [Ars Technica].

The study, published in Science [subscription required], has piqued the interest of astrobiologists who say that extraterrestrial life could resemble this bacteria.

"One question that has arisen when considering the capacity of other planets to support life is whether organisms can exist independently, without access even to the Sun," says [lead researcher Dylan] Chivian. "The answer is yes and here's the proof." ... Chris McKay, of NASA's Ames Research Center says that D. audaxviator is an amazing discovery, and represents the kind or organism that could survive below the surface of Mars or Saturn's sixth largest moon Enceladus [New Scientist].

D. audaxviator derives energy from the radioactive decay of uranium in surrounding rocks and gets carbon and nitrogen, two of the building blocks of life, either from dissolved gases or by cannibalizing other bacteria.

Jules Verne’s novel Journey to the Center of the Earth inspired part of the name — Candidatus Desulforudis audaxviator — the scientists gave to the newly discovered bacterium.... Audaxviator is Latin for “bold traveler,” from a passage in Verne’s book that translates to “Descend, bold traveler … and you will attain the center of the Earth” [Science News].

Image: Greg Wanger, J. Craig Venter Institute/Gordon Southam, University of Western Ontario