HR: 0800h
AN: B21B-0891    [Abstracts]
TI: Predictive Microbiology in Hydrothermal Ecosystems
AU: * Shock, E L
EM: eshock@asu.edu
AF: Department of Geological Sciences, Arizona State University, Box 1404, Tempe, AZ 85287-1404 United States
AU: * Shock, E L
EM: eshock@asu.edu
AF: Department of Chemistry and Biochemistry, Arizona State University, Box 1604, Tempe, AZ 85287-1604 United States
AU: Holland, M E
EM: melanie.holland@asu.edu
AF: Department of Geological Sciences, Arizona State University, Box 1404, Tempe, AZ 85287-1404 United States
AU: Meyer-Dombard, D
EM: darmeyer@artsci.wustl.edu
AF: Department of Earth and Planetary Sciences, Washington University, Campus Box 1169, 1 Brookings Drive, St. Louis, MO 63130 United States
AU: Amend, J P
EM: amend@levee.wustl.edu
AF: Department of Earth and Planetary Sciences, Washington University, Campus Box 1169, 1 Brookings Drive, St. Louis, MO 63130 United States
AB: Metabolisms of high-temperature microorganisms are not revealed by molecular phylogenies, but, if known, could connect microbial and geochemical processes in hydrothermal ecosystems. Disequilibria among oxidation-reduction reactions, established by kinetic barriers to electron-transfer reactions, provide energy, and life provides the catalyst. In more-or-less closed systems, such as slowly-accumulating detrital sediments, life taps as much energy as conversion efficiency will allow, and many redox couples are driven to near-equilibrium states. In contrast, open systems like hot springs maintain persistent states of redox disequilibria that support highly diverse communities of microorganisms. In Yellowstone National Park hot springs, the magnitude of these redox disequilibria can be predicted based solely on pH, guided by past measurements of hot spring geochemistry. Geochemical diversity at Yellowstone National Park produces hydrothermal ecosystems over a pH range from less than 2 to greater than 8, with associated major and trace element concentration changes. We have assessed the supply of chemical energy in the form of redox reactions that are far from equilibrium in the Fe-S-C-O-H-N system. Field measurements of temperature, pH, dissolved oxygen, total sulfide, nitrate, nitrite, total ammonia, ferrous iron, and bicarbonate alkalinity are combined with lab analyses of sulfate, iron mineralogy, and gas composition (hydrogen, carbon dioxide, methane, carbon monoxide) in a thermodynamic analysis of the state of redox disequilibria in more than 50 hot spring habitats. Initial results (using only inorganic forms of C) yield nearly 200 reactions that are out of redox equilibrium, and which could supply energy if catalyzed. Some of these reactions, such as hydrogen oxidation, are pH independent, and the energy supply is nearly constant at about 24 kcal per mole of electrons over the entire pH range. Other reactions, which are pH dependent, show greater or lesser variations in energy supply as pH changes. As an example, the oxidation of dissolved ferrous iron to goethite varies from 26 kcal per mole of electrons (more energy-yielding than hydrogen oxidation) near pH 8, to 10 kcal per mole of electrons at pH 2. Taken together, these trends provide the first comprehensive framework for predicting which thermophilic metabolisms will prevail in which hydrothermal environments. Merging molecular microbiological methods with this type of predictive geochemical data will produce a new integrated biogeochemical approach to solving problems in microbial ecology.
UR: http://geopig.asu.edu
DE: 8424 Hydrothermal systems (8135)
DE: 4805 Biogeochemical cycles (1615)
DE: 0400 Biogeosciences
DE: 1000 GEOCHEMISTRY (New field, replaces Rock Chemistry)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting