HR: 16:30h
AN: B14A-03    [Abstracts]
TI: Phototrophs vs. chemotrophs: surprising diversity at the intersection of hot springs communities
AU: * Raymond, J
EM: jason.raymond@ucmerced.edu
AF: University of California, Merced, Box 2039, Merced, CA 95363,
AU: Meyer-Dombard, D
EM: drmd@uic.edu
AF: University of Illinois, Chicago, 601 S. Morgan, Chicago, IL 60607,
AU: Shock, E L
EM: everett.shock@asu.edu
AF: Arizona State University, Box 871404, Tempe, AZ 85287,
AB: Access makes hot spring ecosystems ideal for combining geochemical data and thermodynamic models of energy supplies with cultivation-independent studies that shed light on biological diversity and function. We have recently undertaken combined 16S rRNA and metagenomic sampling of multiple communities found along a nearly 40 degree temperature gradient in a geochemically well-characterized alkaline hot spring in Yellowstone National Park (YNP). One unexpected result of this work comes at the so-called photosynthetic fringe, where "hot" chemotrophic metabolism gives way to "cool" phototrophy. This transition occurs between 55 and 73 degrees C in alkaline YNP springs for reasons that are poorly understood. While it is generally observed in other habitats that biodiversity increases as temperature decreases, 16S analysis reveals that diversity peaks at the fringe and tapers off at both higher and lower temperatures. Intriguingly, this increase is above and beyond what would be expected by merging the chemotrophic communities above the fringe with the photosynthetic communities below it, indicating that some facet of this unique intersection is supporting the potential for new niches to arise. Integrating metagenomic data with geochemical analyses offers molecular-level details for understanding how these niches develop and are sustained. The underlying interplay between geochemistry and genomics may well be driving the evolution and distribution of new metabolic capabilities including the presence of deeply branching RuBisCO and pyruvate:ferredoxin oxidoreductase homologs involved in autotrophic carbon fixation.
DE: 0428 Carbon cycling (4806)
DE: 0444 Evolutionary geobiology
DE: 0448 Geomicrobiology
DE: 0450 Hydrothermal systems (1034, 3017, 3616, 4832, 8135, 8424)
DE: 0456 Life in extreme environments
SC: Biogeosciences [B]
MN: 2007 Fall Meeting