HR: 1340h
AN: B53C-1009    [Abstracts]
TI: Ranking Geochemical Energy Availability in Hydrothermal Ecosystems
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: 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: 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: The energy available to hyperthermophilic microorganisms in hot springs can be theoretically estimated using thermodynamic calculations based on geochemical measurements. The relative abundance of different geochemical energy sources (the "ranking" of these reactions) in particular hot springs may provide one explanation for the differences in hot spring microbial communities and also facilitate the culture of ecologically-relevant microorganisms. Geochemical sampling of seven Yellowstone National Park hot springs was repeated five times from 1999 to 2004 with the intent to compare the geochemistry and geochemical energy available to microorganisms. These seven hot springs were located in three separate regions of Yellowstone National Park: three hot springs, including Obsidian Pool, were sampled in the Mud Volcano area; two in the Sylvan Springs area (Gibbon Meadows); and one each in Imperial Meadows and Sentinel Meadows (Lower Geyser Basin). The hot springs were 75 to $93\deg$C (with one $65\deg$C exception) and spanned the bulk of the pH range at Yellowstone (pH 1.8 to 7.6). Geochemical measurements made on hot springs included redox-active species containing C, N, O, H, S, and Fe; these species were measured by field spectrophotometry and ion chromatography of fluid samples and gas chromatographic analysis of gas samples. From these measurements chemical affinities were calculated for 179 inorganic reactions which encompass the suite of autotrophic energy sources potentially available in each pool. Composite affinities for each reaction were compiled for each of the seven primary pools. The composite for each pool was assembled from repeat measurements from the primary pool as well as nearby pools with similar geochemistry. Calculations show that over half of these inorganic reactions could provide enough energy for a microorganism to survive, based on the threshold value of energy required by {it E. coli} (20 kJ per mole of electron pairs). Some microorganisms, including those in syntrophic associations, may have a much lower energetic threshold (near 5 kJ per mole of electron pairs; Jackson and McInerney, 2002, Nature 415:454), which includes another quarter of the calculated reactions. Oxygen is the most energetic electron acceptor in all pools, but the relative ranking of the most energetic reactions changes from pool to pool. Iron-containing reactions are the most sensitive to pH variations. The subtle shifts in the ranking of the energy supplies lead to testable predictions about microbial community structure and function. Some highly energetic reactions correspond to unknown metabolisms; targeting these potential metabolisms with enrichment cultures could expand the range of known thermophiles.
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