Clostridium thermocellum Transcriptomic Profiles after Exposure to Furfural or Heat Stress

Background: The thermophilic anaerobe Clostridium thermocellum is a candidate consolidated bioprocessing (CBP) biocatalyst for cellulosic ethanol production. It is capable of both cellulose solubilization and its fermentation to produce lignocellulosic ethanol. Intolerance to stresses routinely encountered during industrial fermentations may hinder the commercial development of this organism. Results: In this study, C. thermocellum was grown to mid-exponential phase and treated with furfural or heat to a final concentration of 3 g.L-1 or 68°C respectively to investigate physiological and regulatory responses. Samples were taken at 10, 30, 60 and 120 min post-shock, and from untreated control fermentations, for transcriptomic analyses and selected extracellular metabolite determinations and compared to a published dataset from an ethanol stress study. In total 1,474 genes were differentially expressed significantly in at least a single time point for a given stressor. One hundred and forty three common genes were differentially expressed for heat, furfural and ethanol stressors including up-regulated genes encoding DNA repair enzymes, Hsp20, sulfate transporter subunits and enzymes in the sulfate assimilatory pathway. Conclusions: This study has identified C. thermocellum gene regulatory motifs and aspects of physiology and gene regulation for further study. The nexus between future systems biology studies and recently developed genetic tools for C. thermocellum offers the potential for more rapid strain development and for broader insights into this organism’s physiology and regulation. A forty three array study using total RNA recovered from wild-type cultures of Clostridium thermocellum at different time points of 10, 30, 60, and 120 min post-treatment with 3.95 g.L-1 ethanol, 3 g.L-1 furfural or 68°C treatment compred to that of control without treatment. At least two biological replicates were performed for each treatment and control condition.