National Research Program
Arsenic-Metabolizing Bacteria in Extreme Environments
The health of millions of people around the world is at risk from drinking well water contaminated with arsenic. In general, this arsenic has been found to occur naturally, rather than coming from identifiable point sources of pollution. With increasing evidence that mobilization of arsenic from subterranean geologic formations into the aqueous phase is a microbiological phenomenon, USGS scientists and others have been conducting field and laboratory investigations to isolate arsenic metabolizing bacteria from diverse environments and to identify which specific microbiological mechanisms are responsible for arsenic dissolution. Research in hypeprsaline, alkaline enviroments has been supported in part by the National Aeronautics and Space Administration (NASA) since the studies also may serve as a biogeochemical guide in the search for microbial life on other planets.
In 2008, scientists from the USGS and several universities reported a primitive form of photosynthesis in which bacteria were found to use arsenic instead of water for photosynthesis (Kulp et al, 2008). This anaerobic photosynthetic oxidation of As(III) may have been an essential mechanism for establishing and maintaining the arsenic cycle on the ancient anoxic Earth.
And in December 2010, a NASA scientist and her colleagues from USGS and elsewhere reported (Wolfe-Simon et al, in advance of print in Science Express) a bacterium that can grow by using arsenic instead of phosphorus. They report that the bacterium, strain GFAJ-1 isolated from Mono Lake, California, substitutes arsenic for phosphorus to sustain its growth. Their data show evidence for arsenate in nucleic acids and proteins that normally contain phosphate, a finding that might have profound evolutionary and geochemical significance.
Kulp, T.R., Hoeft, S.E., Asao, M., Madigan, M.T., Hollibaugh, J.T., Fisher, J.C., Stolz, J.F., Culbertson, C.W., Miller, L.G. and Oremland, R.S., 2008, Arsenic(III) fuels anoxygenic photosynthesis in hot spring biofilms from Mono Lake, California: Science v. 321, p. 967 - 970.Wolfe-Simon, F., Blum, J.S., Kulp, T.R.,Gordon, G.W., Hoeft, S.E., Pett-Ridge, J., Stolz, J.F., Webb, S.M., Weber, P.K., Davies, P.C.W., Anbar, A.D., and Oremland, R.S., in press, A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus: Science. DOI: 10.1126/science.1197258