9615830 Wirsen New processes of sulfur metabolism are continuously being described, yet aspects of chemolithotrophic metabolism of marine sulfur oxidizers have not been well studied. These organisms may have adaptive mechanisms for energy yielding oxidations in the highly buffered marine environment compared to the extreme acid conditions in which many of these types of organisms grow in freshwater environments. A new aspect of oxidation of polymetal sulfides has recently been described which demonstrates this process is carried out by natural marine populations and by pure cultures at the near neutral pH of seawater. Isolates of marine non- acidophilic sulfur oxidizers from different hydrothermal vent habitats will be studied to determine the mechanism of this process, what component(s) of metal sulfides (e.g. pyrite, chalcopyrite) are utilized for energy, what role abiological solubilization plays, what the intermediates and end products of the oxidation are, and what some of the limitations are that can control this process of polymetal sulfide oxidation in the vent environment. Radioisotopic procedures to follow carbon fixation; chemical assays and EDX to determine substrates, intermediates and endproducts; factors controlling growth such as pH and oxygen; epifluorescent microscopy for total direct counts and attached cells; and traditional cultural techniques will all be used in addressing the above objectives. It is likely that this process of circumneutral metal sulfide oxidation may play a significant role in augmenting abiological processes of sulfide geochemistry and mineralization. That the massive accumulations of metal sulfides which are deposited around hydrothermal vent areas constitute a new and important long term supply of chemolithotrophic energy for autotrophic processes necessitates a clear and better understanding of the importance of this mechanism in the overall transfer of geothermal into biochemical energy.
