Desulfonatronum thiodismutans is a unique microorganism that is one of many inhabitants of the mud in Mono Lake. Although Mono Lake is an extreme aqueous environment in California that may appear incapable of sustaining life, a particular group of microbes in the lake demonstrate the importance of life cycles and interdependence.
Richard Hoover, a microbiologist at the NASA Marshall Space Flight Center, is interested in studying the interdependence of microorganisms, particularly those that thrive in extreme environments. Understanding how microbes are capable of living in extreme conditions is important to NASA’s mission of finding life on Mars, where extreme conditions are prevalent. In his quest at Mono Lake, Richard Hoover discovered Desulfonatronum thiodismutans in samples of black mud sediments with a pH near 9.9 that smelled of sulfide.
D. thiodismutans is a microorganism that thrives in extreme environments such as Mono Lake. It is an alkaliphilic, sulfate-reducing bacterium that carries out chemo-litho-autotrophic metabolism. In addition, it is gram-negative with vibrio-shaped cells and is motile by a single polar flagellum.
Other organisms that flourish in the extreme environment of Mono Lake depend on D. thiodismutans for survival. This notorious microbe is unique because it can grow on hydrogen without an organic source of carbon. Hydrogen and sulfur compounds are readily available in the minerals of the mud. D. thiodismutans obtains its energy by metabolizing these compounds and creates sugars and other organic materials, which are then utilized by co-inhabitants of Mono Lake. Two such bacteria, discovered before D. thiodismutans by Hoover and his colleagues, are Tindallia californiensi and Spirochaeta americana. These microbes are also extremophiles, but they are known as organotrophs because they ingest organic materials. Lucky for them, D. thiodismutans has organic material to spare and doesn’t mind helping a fellow microbe. These three microbes are able to thrive together in a dark, extreme environment by utilizing the resources produced by each organism in a bacterial cycle.
T. californiensis consumes simple amino acids and other chemicals to produce complex organic compounds (such as sugars, fats, and proteins). Subsequently, S. americana uses the complex organic compounds provided by T. californiensis and excretes hydrogen and other gases. Thus, D. thiodismutans contributes organic materials to the bacterial cycle and, in return, T. californiensis replenishes hydrogen for D. thiodismutans. When the organisms die, they return minerals to the soil and complete the cycle.
The hydrogenase enzyme of D. thiodismutans is of interest to determine how hydrogenases respond to high salt concentrations and high pH. In recent studies, the hydrogenase of D. thiodismutans was found to be tolerant to high sodium salt concentrations and resistant to high pH. Since hydrogenase is such a major enzyme, this information could be beneficial for future applications in biotechnology.
Desulfonatronum thiodismutans and the other microorganisms in the bacterial anaerobic community of Mono Lake demonstrate that even under extreme conditions, leading an interlinked and interdependent life is crucial for survival. This mechanism of survival is very common among all lifeforms, including plants and animals, because developing interdependent relationships and finding a suitable niche allows a species to thrive. Due to this tendency for organisms to depend on other organisms for survival, it is likely to discover multiple species in any environment – no matter how extreme it might be.
References
Detkova, Pikuta, Hoover. “Salt-tolerant and high-pH-resistant hydrogenase from the haloalkaliphilic, sulfate-reducing bacterium Desulfonatronum thiodismutans.” Smithsonian/NASA ADS. November 2004. <http://adsabs.harvard.edu/cgi-bin/nphbib_query?bibcode=2004SPIE.5555..191D&db_key=AST&data_type=HTML&format=>
Koczor, Ron. “Extreme Ecosystems.” Science at NASA. 13 May 2004.
<http://science.nasa.gov/headlines/y2004/13may_ecosystem.htm>Perlman, David. “From outer space to inner Earth Microbe hunter digs for clues to exotic life in Mono Lake.” SFGate.com. 1 Sept. 2003.
<http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2003/09/01/MN84192.DTL>Pikuta et al. “Desulfonatronum thiodismutans sp. nov., a novel alkaliphilic, sulfate-reducing bacterium capable of lithoautotrophic growth.” International Journal of Systematic and Evolutionary Microbiology. 24 January 2003.
<http://ijs.sgmjournals.org/cgi/content/full/53/5/1327>*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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