Saturday, October 11, 2008

Single Species Ecosystem At The Earth's Core

The first ecosystem ever found having only a single biological species has been discovered 2.8 km beneath the surface of the earth in the Mponeng gold mine near Johannesburg, South Africa. There the rod-shaped bacterium Desulforudis audaxviator exists in complete isolation, total darkness, a lack of oxygen, and 60-degree-Celsius heat.

D. audaxviator survives in a habitat where it gets its energy not from the sun but from hydrogen and sulfate produced by the radioactive decay of uranium. Living alone, D. audaxviator must build its organic molecules by itself out of water, inorganic carbon, and nitrogen from ammonia in the surrounding rocks and fluid. During its long journey to the extreme depths, evolution has equipped the versatile spelunker with genes – many of them shared with archaea, members of a separate domain of life unrelated to bacteria – that allow it to cope with a range of different conditions, including the ability to fix nitrogen directly from elemental nitrogen in the environment.

It’s genome contains everything needed for the organism to sustain an independent existence and reproduce, including the ability to incorporate the elements necessary for life from inorganic sources, move freely, and protect itself from viruses, harsh conditions, and nutrient-poor periods by becoming a spore.

Dylan Chivian coined the name “audaxviato” from a phrase found in Jules Verne's Journey to the Center of the Earth, in a message – "Conveniently in Latin," says Chivian -- deciphered by Verne's protagonist, Professor Lidenbrock, which reads in part, "descende, Audax viator, et terrestre centrum attinges." It means "descend, Bold traveler, and attain the center of the Earth." link
Environmental genomics reveals a single-species ecosystem deep within the Earth. D. Chivian et al.. 2008. Science 322.