H+ equivalent elimination by the tube-worm Riftia pachyptila
In: Cahiers de Biologie Marine. Station Biologique de Roscoff: Paris. ISSN 0007-9723; e-ISSN 2262-3094, more Also appears in:(1998). Proceedings of the First International Symposium on Deep-Sea Hydrothermal Vent Biology: Funchal, Madeira, Portugal 20-24 October 1997. Cahiers de Biologie Marine, 39(3-4). Station Biologique de Roscoff: Roscoff. 219-392 pp., more |   |
| Authors | | Top | - Girguis, P.R.
- Childress, J.J.
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| Abstract | The tube-worm Riftia pachyptila Jones, 1981 is one of the most prominent members of the hydrothermal vent community. This organism harbours chemolithoautotrophic bacteria deep within its body in a specialized organ known as the trophosome. The bacteria are capable of sulphide oxidation for energy production and inorganic carbon fixation. As a consequence of its morphology, the tube-worm must provide its symbionts with the compounds required for autotrophy (e.g. inorganic carbon and sulphide). Recent studies have demonstrated that CO2 is the primary species of inorganic carbon (Ci) which is assimilated by the tube-worm (Goffredi et al., 1997). It is posited that the uptake of CO2 takes place across the respiratory surfaces via passive diffusion. The influx of CO2 is expected to shift the Ci equilibrium, resulting in the production of bicarbonate and proton equivalents. Acidification of the tubeworm's body fluids would diminish the gradient favouring the passive influx of CO2. Thus, we believe that the maintenance of an alkaline internal pH (relative to the environment) is fundamental to Ci uptake.In addition, sulphide metabolism would also result in a production of proton equivalents (Girguis & Childress, in prep). Depending upon which species is acquired, the uptake of sulphide could produce one proton per sulphide. Furthermore, the oxidation of H2S or HS- to sulphate (SO sub4) will result in the production of one or two protons per sulphide. Due to the substantial rates of carbon fixation and sulphide oxidation, the production of proton equivalents should be considerable. It was our intention to determine the rates of proton elimination as a function of inorganic carbon acquisition and sulphide oxidation, and to assess the dependency of these uptake rates on the maintenance of proton elimination. |
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