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article imageAncient Bacteria Uses Arsenic to Grow

By Bob Ewing     Aug 22, 2008 in Environment
Scientists have discovered ancient bacteria that rely on arsenic rather than water to grow during photosynthesis. This process probably dates back a few billion years.
Everything has a purpose, a reason for being part of an ecosystem. Most often it is to serve as nourishment for something else and keep the cycle of life turning.
Even arsenic has its place and scientists have discovered ancient bacteria that rely on arsenic, rather than water, to grow during photosynthesis.
Analysis indicates this process probably dates back a few billion years.
Arsenic is a chemical element and is a natural constituent of the Earth's crust. It occurs naturally in rocks, soil, water, air, plants and animals. When in the natural environment, arsenic usually binds to other molecules, such as those found in soils, and does not tend to travel very far. The average concentration of arsenic in soils in the United States varies considerably. Arsenic can be released into the environment through natural processes such as volcanic activity, erosion of rocks and forest fires.
Human actions, such as agricultural practices, mining, smelting and combustion of fossil fuels also contribute to arsenic releases in the environment.
An important new dimension has been added to the arsenic cycle and this discovery brings to light a previously unsuspected process that may have been essential for establishing the arsenic cycle on the ancient Earth. The results are published in Science.
Two small hot spring-fed ponds on the south-eastern shore of Paoha Island in Mono Lake, CA were sampled. The springs were termed "green" and "red" based on the colors of the microbiological films in the pools that were studied.
The samples from these springs oxidized the highly toxic Arsenic(III) to the less toxic and less mobile Arsenic(V) by light-dependent photosynthetic reaction that occurred in the absence of oxygen.
In addition, the scientists also isolated a photosynthetic bacterium that demonstrated As(III)-dependent growth under anoxic ( absence or near absence of oxygen) conditions.
NASA's Exobiology Program helped to fund the research along with the USGS. Collaborating colleagues in the diverse, team-oriented aspects of the experimental work were from Duquesne University (Prof. J.F. Stolz; Pittsburgh, PA) University of Georgia (Prof. J.T. Hollibaugh and Dr. J.Fisher); Athens, GA), Southern Illinois University (Prof. M. Madigan, and Dr. M.Asao), the USGS in Menlo Park, CA (Dr. R.S. Oremland, Dr. T.R. Kulp, S.E. Hoeft, and L.G. Miller) and the USGS Water Science Center in Maine (C.W. Culbertson).
More about Bacteria, Arsenic, Photosynthesis
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