HR: 1330h
AN: B12A-0760    [PDF]
TI: The Majority of Free-Living Autotrophic Bacteria use the Reductive TCA Cycle for Carbon Fixation at Deep-Sea Hydrothermal Vents
AU: * Campbell, B J
EM: bjc@udel.edu
AF: University of Delaware, College of Marine Studies, 700 Pilottown Road, Lewes, DE 19958
AU: Cary, C
EM: caryc@udel.edu
AF: University of Delaware, College of Marine Studies, 700 Pilottown Road, Lewes, DE 19958
AB: Deep-sea hydrothermal vents support large micro and macroscopic communities, without the input of photosynthesis. Autotrophic production at these vents is based on hydrothermal vent fluid chemistry. Primary production has been thought to occur mainly via hydrogen sulfide oxidation through the Calvin-Benson pathway, as measured by the presence of Rubisco in endosymbionts of several invertebrate hosts. Recently, we characterized two fosmids from a large insert library of the epsilon Proteobacterial episymbionts of Alvinella pompejana. Both contained sequences encoding ATP citrate lyase, a key enzyme in the reverse TCA cycle, an alternate carbon dioxide fixation pathway. Previous investigators have demonstrated the dominance of the epsilon subdivision in the free-living bacterial communities at hydrothermal vents. Based on these results, our working hypothesis is: The rTCA cycle is the dominant pathway for carbon fixation in the free-living bacterial communities at hydrothermal vents. A selection of free-living bacterial communities from various geographic locations (9N, East Pacific Rise and Guaymas Basin) were screened for the presence, diversity and expression (via RT-PCR) of Rubisco (forms I and II) and ATP citrate lyase. Our results indicate that the ATP citrate lyase gene is diverse and is consistently expressed in several types of vent communities. The two forms of Rubisco are not consistently present or expressed in the same environments. These results indicate that chemoautotrophic production in the free-living bacterial communities at deep-sea hydrothermal vents is dominated by bacteria that utilize the rTCA cycle, and parallels the phylogenetic dominance of members of the epsilon subdivision of Proteobacteria.
DE: 1020 Composition of the crust
DE: 3015 Heat flow (benthic) and hydrothermal processes
DE: 3035 Midocean ridge processes
DE: 4815 Ecosystems, structure and dynamics
DE: 7218 Lithosphere and upper mantle
SC: Biogeosciences [B]
MN: 2003 Fall Meeting