Rising global demand for energy coupled with recent supply-side instability in the petroleum market have prompted renewed calls for the development of alternative fuel sources to reduce America’s dependence on foreign oil. One such alternative, bioproduced ethanol derived from cellulosic plant materials, has been designated by the President of the United States and the US Department of Energy (DOE) as a primary alternative for immediate and long-term replacement of fossil fuels (1). To address this mission, the Clostridium Sequencing Consortium (CSC) proposes the complete genomic sequencing of 20 strains of bacteria from the Class Clostridia. These strains were chosen for their proven ability to degrade complex cellulosic polymers, to ferment a variety of cellulosic degradation byproducts to ethanol and to produce beneficial industrial compounds in addition to ethanol. The chosen strains are distributed throughout the Class Clostridia with the majority of strains chosen from the genera Thermoanaerobacter, Thermoanaerobacterium and Clostridium. Strains were selected based on distinct biochemical, physiological and ecological characteristics designed to maximize the information obtained for the core bioenergy-related activities. Sequencing of these 20 strains will greatly advance understanding of the biochemistry, physiology, ecology, evolution and speciation of Clostridia species and will provide a critical mass of genomic data for future systems biology research efforts devoted to biofuels research. Thermoanaerobacter brockii subsp. finnii Ako-1, isolated from lake sediment sludge, is an efficient producer of ethanol from xylose (2,3). Ethanol is the major end product of fermentation from glucose and xylose, but switches to acetate under thiosulfate-respiring conditions (4). Respiration of thiosulfate is accompanied by increased growth rates and yields, suggesting an increased rate of substrate-level phosphorylation. In addition, thiosulfate reduction can be linked to H2 oxidation which serves to alleviate the toxic effects of H2 concentrations (5). As such, thiosulfate- reducing species may play a significant role in carbon flux in sulfidogenic environments (4). Efforts are currently underway in the Wiegel laboratory to clarify the taxonomy of this genus. References 1. Farrell, A. E., Plevin, R. J., Turner, B. T., Jones, A. D., O'Hare, M. & Kammen,
D. M. (2006) Science 311, 506-508. |
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