Tuesday, April 30, 2013
Exhibit Hall
Clostridium stercorarium subsp. stercorarium DSM8532 is an anaerobic thermophile with a well-characterized complement of acellulosomal cellulases and hemicellulases. Since the organism is known as a preferential hemicellulose-degrader, understanding xylose metabolism is likely to be informative regarding potential designer consortia for consolidated bioprocessing of lignocellulose for biofuels production. Central metabolism for this organism has not been described, therefore the goal of this study was to characterize end products of C. stercorarium growing on xylose in the context of whole genome pyrosequencing (Roche/454) and mass spectrometry-based proteomics. End products were carbon dioxide, hydrogen, ethanol, acetate and lactate on both xylose and cellobiose, with simultaneous depletion of these substrates indicating co-utilization of these substrates. A complete genome sequence was generated using newbler assembly software coupled with in silico gap-filling, gap-specific primer design and Sanger sequencing. Gene expression for glycolysis and pyruvate catabolism pathways was confirmed by proteomic analysis, however no pentolytic transaldolase was observed in the genome. Peptides from the bifunctional acetaldehyde/alcohol dehydrogenase (adhE) and pyruvate dikinase were highly abundant, suggesting a central role for these enzymes in pyruvate catabolism. Quantitative proteomics (iTraq) revealed only a small subset of proteins that were differentially abundant when comparing cellobiose- vs. xylose-grown cells. Lack of transaldolase has been observed in genome sequences for other cellulolytic clostridia, however not in an organism where xylose utilization has been directly observed. Further work will be required to address alternative pathways of xylose utilization and elucidate a potential role for this organism in designer consortia for biofuels production.