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Title: Rex in Caldicellulosiruptor bescii: Novel regulon members and its effect on the production of ethanol and overflow metabolites

Rex is a global redox-sensing transcription factor that senses and responds to the intracellular [NADH]/[NAD+] ratio to regulate genes for central metabolism, and a variety of metabolic processes in Gram-positive bacteria. We decipher and validate four new members of the Rex regulon in Caldicellulosiruptor bescii; a gene encoding a class V aminotransferase, the HydG FeFe Hydrogenase maturation protein, an oxidoreductase, and a gene encoding a hypothetical protein. Structural genes for the NiFe and FeFe hydrogenases, pyruvate:ferredoxin oxidoreductase, as well as the rex gene itself are also members of this regulon, as has been predicted previously in different organisms. A C. bescii rex deletion strain constructed in an ethanol-producing strain made 54% more ethanol (0.16 mmol/L) than its genetic parent after 36 hr of fermentation, though only under nitrogen limited conditions. Metabolomic interrogation shows this rex-deficient ethanol-producing strain synthesizes other reduced overflow metabolism products likely in response to more reduced intracellular redox conditions and the accumulation of pyruvate. In conclusion, these results suggest ethanol production is strongly dependent on the native intracellular redox state in C. bescii, and highlight the combined promise of using this gene and manipulation of culture conditions to yield strains capable of producing ethanol at higher yieldsmore » and final titer.« less
Authors:
ORCiD logo [1] ;  [2] ;  [3] ;  [2] ; ORCiD logo [3] ; ORCiD logo [3] ;  [3] ; ORCiD logo [3] ; ORCiD logo [4] ; ORCiD logo [5]
  1. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemical and Biomolecular Engineering; Univ. of Tennessee, Knoxville, TN (United States). Bredesen Center for Interdisciplinary Graduate Research and Education; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Sciences Center
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Sciences Center; Univ. of Georgia, Athens, GA (United States). Dept. of Genetics
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Sciences Center; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences Division
  4. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemical and Biomolecular Engineering; Univ. of Tennessee, Knoxville, TN (United States). Bredesen Center for Interdisciplinary Graduate Research and Education; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Sciences Center; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences Division
  5. Univ. of Tennessee, Knoxville, TN (United States). Bredesen Center for Interdisciplinary Graduate Research and Education; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Sciences Center; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences Division
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Published Article
Journal Name:
MicrobiologyOpen
Additional Journal Information:
Journal Volume: 0; Journal Issue: 0; Journal ID: ISSN 2045-8827
Publisher:
Wiley
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:
59 BASIC BIOLOGICAL SCIENCES; Caldicellulosiruptor bescii; consolidated bioprocessing; ethanol; Rex
OSTI Identifier:
1438932
Alternate Identifier(s):
OSTI ID: 1438933; OSTI ID: 1461944

Sander, Kyle B., Chung, Daehwan, Hyatt, Doug, Westpheling, Janet, Klingeman, Dawn M., Rodriguez, Miguel J., Engle, Nancy L., Tschaplinski, Timothy J., Davison, Brian H., and Brown, Steven D.. Rex in Caldicellulosiruptor bescii: Novel regulon members and its effect on the production of ethanol and overflow metabolites. United States: N. p., Web. doi:10.1002/mbo3.639.
Sander, Kyle B., Chung, Daehwan, Hyatt, Doug, Westpheling, Janet, Klingeman, Dawn M., Rodriguez, Miguel J., Engle, Nancy L., Tschaplinski, Timothy J., Davison, Brian H., & Brown, Steven D.. Rex in Caldicellulosiruptor bescii: Novel regulon members and its effect on the production of ethanol and overflow metabolites. United States. doi:10.1002/mbo3.639.
Sander, Kyle B., Chung, Daehwan, Hyatt, Doug, Westpheling, Janet, Klingeman, Dawn M., Rodriguez, Miguel J., Engle, Nancy L., Tschaplinski, Timothy J., Davison, Brian H., and Brown, Steven D.. 2018. "Rex in Caldicellulosiruptor bescii: Novel regulon members and its effect on the production of ethanol and overflow metabolites". United States. doi:10.1002/mbo3.639.
@article{osti_1438932,
title = {Rex in Caldicellulosiruptor bescii: Novel regulon members and its effect on the production of ethanol and overflow metabolites},
author = {Sander, Kyle B. and Chung, Daehwan and Hyatt, Doug and Westpheling, Janet and Klingeman, Dawn M. and Rodriguez, Miguel J. and Engle, Nancy L. and Tschaplinski, Timothy J. and Davison, Brian H. and Brown, Steven D.},
abstractNote = {Rex is a global redox-sensing transcription factor that senses and responds to the intracellular [NADH]/[NAD+] ratio to regulate genes for central metabolism, and a variety of metabolic processes in Gram-positive bacteria. We decipher and validate four new members of the Rex regulon in Caldicellulosiruptor bescii; a gene encoding a class V aminotransferase, the HydG FeFe Hydrogenase maturation protein, an oxidoreductase, and a gene encoding a hypothetical protein. Structural genes for the NiFe and FeFe hydrogenases, pyruvate:ferredoxin oxidoreductase, as well as the rex gene itself are also members of this regulon, as has been predicted previously in different organisms. A C. bescii rex deletion strain constructed in an ethanol-producing strain made 54% more ethanol (0.16 mmol/L) than its genetic parent after 36 hr of fermentation, though only under nitrogen limited conditions. Metabolomic interrogation shows this rex-deficient ethanol-producing strain synthesizes other reduced overflow metabolism products likely in response to more reduced intracellular redox conditions and the accumulation of pyruvate. In conclusion, these results suggest ethanol production is strongly dependent on the native intracellular redox state in C. bescii, and highlight the combined promise of using this gene and manipulation of culture conditions to yield strains capable of producing ethanol at higher yields and final titer.},
doi = {10.1002/mbo3.639},
journal = {MicrobiologyOpen},
number = 0,
volume = 0,
place = {United States},
year = {2018},
month = {5}
}

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