Desulforudis audaxviator Daniel Roush
Metabolism of all organisms on Earth can be traced back through different pathways to the sun, or this was at least thought to be the case until 2006 when microbiologists discovered a completely unique and alien organism in the bottom of a gold mine in South Africa.
Image from NASA
Desulforudis audaxviator was isolated using a new technique called environmental genomics, where a sample of the desired bacteria is removed from the area and completely sequenced. The dominant species will have a substantial amount of genetic material and thus allows for an initial isolation through genetics.
After the initial genetic isolation, many of the interesting features of D. audaxviator have surfaced. The bacterium is gram positive and reduces sulfate in its metabolic path. Along with being an obligate anaerobe, D. audaxviator has a completely new and unique respiration and metabolic system.
When Desulforudis audaxviator was discovered, scientists were puzzled by the fact that the bacterium was completely isolated from sunlight and photosynthetic compounds, but had managed to survive and flourish in isolation. After a complete sequencing of the bacterium’s genome, it was discovered that the bacteria could fix nitrogen and extract carbon from carbon dioxide along with reducing sulfur. D. audaxviator obtains hydrogen from the radiolysis of water in its environment. All of these unique features contribute to the ability of D. audaxviator to survive as the only organism in its ecosystem.
An analysis of the unique metabolic pathways that D. audaxviator uses to produce energy, it appears that the hydrogen ions created by the radiolysis of water on the exterior of the cell produces the proton motive force needed for ATP synthesis. Along with this environmental proton gradient it appears the organism produces some unique metallic gradients along with a seemingly endless amount of different biosynthesis reactions taking place within the organism.
The discovery of such a unique organism has pioneered new theories in the field of astrobiology. Desulforudis audaxviator has a completely isolated metabolic system and can survive entirely independent of any other organism and without any sunlight. In the right temperature environment and with a hydrogen source, D. audaxviator could theoretically survive in any type of environment with a huge variability in the electron donors it could use for respiration. There are celestial bodies in our own solar system that could be a breeding ground for this type of organism, or similar organisms with the same genetic variability that allows for a self-sustaining ecosystem. NASA has also become interested in D. audaxviator as an example of the possibilities of life on other rocky planets in the universe. With the discovery of water on mars and the possibility that there could also be liquid water on the planet, the probability that an organism like Desulforudis audaxviator could be found is increasing by the day.
With the discovery of Desulforudis audaxviator and the potential for other organisms utilizing the same type of respiration techniques, major steps have been taken in the search for extraterrestrial life. Now that the potential respiratory system has been identified, scientists can begin to search for the subtle cues given off by these organisms on other planets, and the final declaration can be made that we are not alone in the universe.
Image from Environmental Genomics
Environmental Genomics Reveals a Single-Species Ecosystem Deep within Earth Dylan Chivian, Science et al. 322 (2008).
*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.
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