The proposed research program will investigate the biochemical mechanisms used by the extremely thermophilic eubacterium Thermotoga neapolitana to derive energy from the oxidation of carbohydrates and the reduction of elemental sulfur. T. neapolitana grows less efficiently in the absence of elemental sulfur by producing hydrogen as a fermentation endproduct. The regulation of the switching between this hydrogen-generating metabolism and a sulfur-reducing metabolism will be studied by analyzing growth responses and protein profiles of cells grown under different conditions. Other sulfur-containing compounds will be screened for their ability to act as electron acceptors to identify the actual substrate of the electron-donating enzyme(s). The sulfur reduction system will be fractionated to identify its components and determine their location within the cell. The enzymes involved in glucose metabolism will also be investigated briefly to identify the source of the electrons used for sulfur reduction. T. neapolitana belongs to a group of eubacteria that may be the closest living relatives of the ancestral eubacterium. Sulfur reduction may be an ancient physiological trait since it is found in Thermotoga species as well as many archaebacteria. An understanding of this process may reveal how metabolic processes evolved in early microorganisms. In addition, sulfur reduction may have biotechnological applications for the removal of sulfurous compounds from ores, coal and petrochemical products.//
