title: Proteomic profile changes in membranes of ethanol-tolerant Clostridium thermocellum.
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.
authors.affiliation: Department of Chemistry, University of Kentucky, Lexington, KY 40546, USA.
authors.forename: Taufika Islam
authors.initials: TI
authors.lastname: Williams
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Combs
authors.forename: Bert C
authors.initials: BC
authors.lastname: Lynn
authors.forename: Herbert J
authors.initials: HJ
authors.lastname: Strobel
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D048013:Acetivibrio thermocellus / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D000431:Ethanol / Q000494:pharmacology*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D007218:Industrial Microbiology / Q000379:methods; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D040901:Proteomics
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D000431:Ethanol