The extremophile, Desulforudis audaxviator, produce all essential amino acids by developing unique methods of fixing both carbon and nitrogen.

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Few organisms are similar to Desulforudis audaxviator in that they are anaerobic chemolithoautotrophs. In other words, they are able to use inorganic sources of energy (instead of consuming organic molecules as food or using sunlight), fix their own carbon (rather than rely on plants to convert carbon dioxide to organic compounds), and use chemicals other than oxygen for respiration. What's more, D. audaxviator can also fix its own nitrogen and use it to synthesize the entire repertoire of amino acids necessary for life. Taken together, these characteristics mean that D. audaxviator is capable of complete independence from other organisms.

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"2.8-kilometer depth in a South African gold mine…Candidatus Desulforudis audaxviator, composes >99.9% of the microorganisms...Its genome indicates a motile, sporulating, sulfate-reducing, chemoautotrophic thermophile that can fix its own nitrogen and carbon...In addition to elevated temperatures and a lack of O2, conditions within Earth’s crust at depths >1 km are fundamentally different from those of the surface and deep ocean environments. Severe nutrient limitation is believed to result in cell doubling times ranging from 100s to 1000s of years...this organism appeared to possess all of the metabolic capabilities necessary for an independent life-style...radiolytically generated chemical species as providing the energy and nutrients to the system, with formate and H2 as possessing the greatest potential among candidate electron donors, and sulfate (SO4 2–) reduction as the dominant electron-accepting process." (Chivian et al. 2008:275)

"We found all of the processes necessary for life encoded within the genome, including energy metabolism, carbon fixation, and nitrogen fixation...Consistent with the thermodynamic evaluation that SO4 2– offers the most energetically favorable electron acceptor, the genome possesses the capacity for dissimilatory sulfate reduction (DSR)...High potential electrons probably enter primarily via the activity of a variety of hydrogenases acting upon locations where biodensity is high, heterotrophic sources could be used, including recycling of dead cells. At MP104, where biodensity is low, carbon is fixed from inorganic sources....Entry of CO2 substrate into the cell may be accomplished by its anionic species through a putative carbonate adenosine triphosphate (ATP)–binding cassette transporter...Formate and CO may serve as alternate, more direct, carbon sources in other fractures when sufficiently abundant." (Chivian et al. 2008:276)

"[A]n ammonium transporter as well as glutamine synthetase...[allows the organism] to obtain its nitrogen from ammonia without resorting to an energetically costly nitrogenase conversion of N2 to ammonia. Nonetheless, a nitrogenase is present in the genome...D. audaxviator’s ability to colonize independently is also assisted by its possession of all of the amino acid synthesis pathways...D. audaxviator appears capable of sensing nutrients in its environment and possesses flagellar genes to permit motility along chemical gradients...One ability that D. audaxviator is lacking is a complete system for oxygen resistance, suggesting the long-term isolation from O2...This bold traveler...has revealed a mode of life isolated from the photosphere, capturing all of the roles necessary for an independent life-style and showing that it is possible to encode the entire biological component of a simple ecosystem within a single genome." (Chivian et al. 2008:277)

Journal article
Environmental Genomics Reveals a Single-Species Ecosystem Deep Within EarthScienceOctober 10, 2008
D. Chivian, E. L. Brodie, E. J. Alm, D. E. Culley, P. S. Dehal, T. Z. DeSantis, T. M. Gihring, A. Lapidus, L.-H. Lin, S. R. Lowry, D. P. Moser, P. M. Richardson, G. Southam, G. Wanger, L. M. Pratt, G. L. Andersen, T. C. Hazen, F. J. Brockman, A. P. Arkin, T. C. Onstott

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