Why Sequence Bacteria That Reduce Sulfur Compounds? Combustion of sulfur-containing fuels, such as coal, oil, and natural gas, contributes significantly to global environmental problems, such as air pollution and acid rain. In addition, sulfur dioxide also supports reactions that create ozone depletion in the stratosphere. So, removal of sulfur compounds from energy carriers is essential for a clean and healthy environment. A sustainable process to remove these sulfur compounds is the production of elemental sulfur (which can be used as a fertilizer or fungicide) from H2S-containing gas streams by the use of sulfur bacteria under highly alkaline (pH 10) and oxygen-limited conditions. However, the sulfate and thiosulfate byproducts of this process need to be removed from the waste stream prior to disposal. This is done by sulfate- and thiosulfate reducing bacteria in an anaerobic reactor with hydrogen as electron donor. In the complete sulfur-removal process, we use bacteria that were isolated from soda lakes, and so naturally adapted to a life at high pH and high salinity (haloalkaline conditions). This project aims to unravel the whole genomes of three anaerobic haloalkaliphilic bacteria from soda lakes that reduce different sulfur compounds (sulfate, thiosulfate and sulfur/polysulfide) at high pH and high salt concentrations. The overall goal of the project is to obtain a comprehensive understanding of the mechanisms by which these bacteria adapt to extreme haloalkaline conditions, and to use this information for improving the removal of sulfur compounds from wastewater and energy carriers. Besides enabling future comparative, structural, and functional genomics studies, the resulting sequences will allow researchers to create genomic tools, such as DNA microarrays, to study the diversity and physiology of these microorganisms in natural and engineered ecosystems. These tools are essential to study the performance of these bacteria in the removal of reduced sulfur compounds from industrial waste streams and energy carriers (e.g., natural gas and syngas). In addition, genomic information about bacteria involved in the reductive part of the sulfur cycle will nicely complement genomic information about the two haloalkaliphilic sulfur-oxidizing Thioalkalivibrio species that are currently been sequenced by the DOE- JGI, thus allowing the complete desulfurization process to be studied and optimized.

Principal Investigators: Gerard Muyzer and Dimitri Sorokin (Delft Univ. of Technology), Fons Stams (Wageningen Univ.), and Roland Siezen (Radboud Univ.)