New Microorganism Discovered that Survives on Arsenic in an Extremely Harsh Environment

Searles Lake, California, where USGS scientists discovered a microorganism that "breathes" using arsenic instead of oxygen (Click on photo for larger version)

A first glance at Searles Lake, California, one would assume that nothing could live in water that is ten times saltier and 70 times more caustic (alkaline, pH 9.8) than seawater, and is loaded with toxic arsenic (approximately 300 mg/L total arsenic). U.S. Geological Survey (USGS) scientists have shown that assumption to be wrong. The scientists have isolated a microorganism from Searles Lake that not only tolerates these ultra extreme conditions, but uses arsenic to "breathe." The microbes gain energy by reducing As(V) (arsenate) to the more toxic As (III) (arsenite) by transferring two electrons to the As(V) (arsenic is acting as an electron acceptor). Evidence for the opposite biochemical reaction, namely the use of As(III) as an electron donor with oxygen as the electron acceptor was also detected. The scientists hope this research will lead to an understanding of how similar microbes in less intense environments, such as a drinking-water aquifer, could be used to remove toxic arsenic from water. This could benefit many places around the world that are plagued with high concentrations of arsenic in drinking-water sources. These newly discovered microbes are also of interest to scientists that are looking for analogs here on earth for life forms on other planets. Dense brines similar to the waters of Searles Lake are hypothesized to exist on other planets or moons, such as within or below the Martian soils, or under the ice crust of Europa (a moon of Jupiter).

Reference

• Oremland, R.S., Kulp, T.R., Blum, J.S., Hoeft, S.E., Baesman, S., Miller, L.G., and Stoltz, J.F., 2005, A microbial arsenic cycle in a salt-saturated, extreme environment: Science, v. 308, p. 1305-1308.

More Information

• Thriving in the Unsurvivable, USGS Science Feature
• Arsenic Eating Microbe Discovered, by Richard Harris, National Public Radio, All Things Considered, May 26, 2005 (Listen)
• Microbial Biogeochemistry of Aquatic Environments
• Oremland, R.S., and Stolz, J.F., 2005, Arsenic, microbes, and contaminated aquifers: Trends in Microbiology, v. 13, no. 2, p. 45-49, doi: 10.1016/j.tim.2004.12.002.
• Oremland, R.S., and Stolz, J.F., 2003, The ecology of arsenic: Science, v. 300, no. 5621, p. 939-944, doi: 10.1126/science.1081903.
• Oremland, R.S., Stolz, J.F., and Hollibaugh, J.T., 2004, The microbial arsenic cycle in Mono Lake, California: FEMS Microbiology Ecology, v. 48, no. 1, p. 15-27, doi: 10.1016/j.femsec.2003.12.016.

Related Headlines

• What Mobilizes Arsenic in Ground Water
• USGS Patents Bioreactors that Treat Nitrate and Methyl Bromide Contamination
• Land-Use Activities Release Naturally Occurring Arsenic
• Scientists Discover Analog for Extraterrestrial Life in Idaho Hot Spring

USGS Information on Arsenic

• Landfill Leachate Mobilizes Arsenic Bound in Aquifer Sediments: Saco, Maine
• USGS Arsenic Studies Group
• Arsenic in Ground Water of the United States, National Water-Quality Assessment
• Arsenic and Old Waste
• Geochemistry of Arsenic, in Arsenic in Ground Water of the Willamette Basin, Oregon, Water-Resources Investigations Report 98-4205
• Arsenic Statistics and Information, USGS Minerals Information

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