Abstract
Clostridium thermocellum, a cellulolytic, thermophilic anaerobe, has potential for commercial exploitation in converting fibrous biomass to ethanol. However, ethanol concentrations above 1% (w/v) are inhibitory to growth and fermentation, and this limits industrial application of the organism. Recent work with ethanol-adapted strains suggested that protein changes occurred during ethanol adaptation, particularly in the membrane proteome. A two-stage Bicine-doubled sodium dodecyl sulfate-polyacrylamide gel electrophoresis protocol was designed to separate membrane proteins and circumvent problems associated with membrane protein analysis using traditional gel-based proteomics approaches. Wild-type and ethanol-adapted C. thermocellum membranes displayed similar spot diversity and approximately 60% of proteins identified from purified membrane fractions were observed to be differentially expressed in the two strains. A majority (73%) of differentially expressed proteins were down-regulated in the ethanol-adapted strain. Based on putative identifications, a significant proportion of these down-regulated proteins were involved with carbohydrate transport and metabolism. Approximately one-third of the up-regulated proteins in the ethanol-adapted species were associated with chemotaxis and signal transduction. Overall, the results suggested that membrane-associated proteins in the ethanol-adapted strain are either being synthesized in lower quantities or not properly incorporated into the cell membrane.
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Acknowledgements
These authors thank the University of Kentucky Mass Spectrometry Facility (http://www.rgs.uky.edu/ukmsf) for laboratory resources. This work was supported by the National Research Initiative of the USDA-CSREES, Grant # 2004-35504-14678.
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Williams, T.I., Combs, J.C., Lynn, B.C. et al. Proteomic profile changes in membranes of ethanol-tolerant Clostridium thermocellum . Appl Microbiol Biotechnol 74, 422–432 (2007). https://doi.org/10.1007/s00253-006-0689-7
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DOI: https://doi.org/10.1007/s00253-006-0689-7