Felbeck 9314525 Free-living and symbiotic bacteria at deep-sea hydrothermal vents use the sulfide formed by geothermal processes as an energy source for chemoautotrophic processes. In order to describe the flow of carbon in a vent community, information is required on how inorganic carbon (CO2) is originally incorporated into organic compounds, and with which energy sources. It's also important to understand the mechanism by which this carbon is eventually transferred from vent bacteria to rest of the community, in particular the hydrothermal-vent tubeworm Riftia pachyptila. Therefore, this project will focus on three research objectives: (1) quantify the transport of CO2 as organic molecules in the blood R. pachyptila; (2) trace the fate of succinate, the molecule transferred from bacteria to their hosts as well as the organic acid carrying the largest proportion of external CO2 in the blood; and (3) determine the relative importance of two alternative electron acceptors for sulfide oxidation, e.g., oxygen and nitrate respiration in R. pachyptila. The results of this research will delineate the important biochemical pathways and mechanisms involved in the synthesis of organic matter by vent communities, which is central to understanding chemoautotrophic processes at deep-sea hydrothermal vents. ***
