Aspects of life development at deep sea hydrothermal vents.

Hydrothermal vent organisms are living in an unexpected deep-sea environment, several thousand meters below the surface, where the earth's crustal plates are spreading apart. The vent fluids are usually hot (350 degrees C), anoxic, and contain high concentrations of hydrogen sulfide. This environment may be considered as extreme given the pressure, the high temperature, the chemical toxicity of the fluids, and the total lack of photosynthetic production for animal nutrition. The recent discovery of the unique fauna of the hydrothermal vent communities has brought an unexpected mode of animal nutrition in which chemoautotrophic bacterial symbionts are maintained within specialized cells of the host animal. The bacterial symbionts obtain energy by oxidizing reduced sulfur compounds from the environment. A portion of this fixed carbon is used by the eukaryotic host. The present review will focus on four of the main topics studied on the paradigmatic vent organism Riftia pachyptila, a giant gutless tube worm: 1) the chemoautotrophic symbiosis, 2) the toxicity of hydrogen sulfide, 3) the characteristics of the extracellular matrices of the worms, especially data obtained on collagens, and 4) the influence of temperature and pressure on worm biology.