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Title: Improved growth rate in Clostridium thermocellum hydrogenase mutant via perturbed sulfur metabolism

Background: Metabolic engineering is a commonly used approach to develop organisms for an industrial function, but engineering aimed at improving one phenotype can negatively impact other phenotypes. This lack of robustness can prove problematic. Cellulolytic bacterium Clostridium thermocellum is able to rapidly ferment cellulose to ethanol and other products. Recently, genes involved in H 2 production, including the hydrogenase maturase hydG, were deleted from the chromosome of C. thermocellum. While ethanol yield increased, the growth rate decreased substantially compared to wild type. Results: Addition of 5 mM acetate to the growth medium improved the growth rate in C. thermocellum ΔhydG, whereas wild type remained unaffected. Transcriptomic analysis of the wild type showed essentially no response to the addition of acetate. However, in C. thermocellum ΔhydG, 204 and 56 genes were significantly differentially regulated relative to wild type in the absence and presence of acetate, respectively. Genes Clo1313_0108-0125, which are predicted to encode a sulfate transport system and sulfate assimilatory pathway, were drastically up-regulated in C. thermocellum ΔhydG in presence of added acetate. A similar pattern was seen with proteomics. Further physiological characterization demonstrated an increase in sulfide synthesis and elimination of cysteine consumption in C. thermocellum ΔhydG. In conclusion, sulfurmore » metabolism is perturbed in C. thermocellum ΔhydG, possibly to increase flux through sulfate reduction to act as an electron sink to balance redox reactions.« less
Authors:
 [1] ;  [2] ; ORCiD logo [3] ; ORCiD logo [2] ;  [2] ;  [2] ; ORCiD logo [3] ; ORCiD logo [2] ; ORCiD logo [2]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences Division; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center; Indian Inst. of Technology Delhi, Hauz Khas, New Delhi (India)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences Division; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Biotechnology for Biofuels
Additional Journal Information:
Journal Volume: 10; Journal Issue: 1; Journal ID: ISSN 1754-6834
Publisher:
BioMed Central
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; Cellulosic ethanol; Clostridium thermocellum; Redox balance; Metabolic engineering; Sulfate reduction
OSTI Identifier:
1393809