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Title: Isotope-Assisted Metabolite Analysis Sheds Light on Central Carbon Metabolism of a Model Cellulolytic Bacterium Clostridium thermocellum

Cellulolytic bacteria have the potential to perform lignocellulose hydrolysis and fermentation simultaneously. The metabolic pathways of these bacteria, therefore, require more comprehensive and quantitative understanding. Using isotope tracer, gas chromatography-mass spectrometry, and metabolic flux modeling, we decipher the metabolic network of Clostridium thermocellum, a model cellulolytic bacterium which represents as an attractive platform for conversion of lignocellulose to dedicated products. We uncover that the Embden-Meyerhof-Parnas (EMP) pathway is the predominant glycolytic route whereas the Entner-Doudoroff (ED) pathway and oxidative pentose phosphate pathway are inactive. We also observe that C. thermocellum's TCA cycle is initiated by both Si- and Re-citrate synthase, and it is disconnected between 2-oxoglutarate and oxaloacetate in the oxidative direction; C. thermocellum uses a citramalate shunt to synthesize isoleucine; and both the one-carbon pathway and the malate shunt are highly active in this bacterium. To gain a quantitative understanding, we further formulate a fluxome map to quantify the metabolic fluxes through central metabolic pathways. This work represents the first global in vivo investigation of the principal carbon metabolism of C. thermocellum. In conclusion, our results elucidate the unique structure of metabolic network in this cellulolytic bacterium and demonstrate the capability of isotope-assisted metabolite studies in understanding microbial metabolismmore » of industrial interests.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ; ORCiD logo [1] ;  [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Report Number(s):
NREL/JA-2700-72400
Journal ID: ISSN 1664-302X
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
Frontiers in Microbiology
Additional Journal Information:
Journal Volume: 9; Journal ID: ISSN 1664-302X
Publisher:
Frontiers Research Foundation
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Fuel Cell Technologies Office (EE-3F); USDOE National Renewable Energy Laboratory (NREL), Laboratory Directed Research and Development (LDRD) Program
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; 13C-isotope tracer; cellulolytic bacteria; citrate synthase; glycolytic pathways; isoleucine biosynthesis; metabolic flux analysis; tricarboxylic acid cycle
OSTI Identifier:
1471551

Xiong, Wei, Lo, Jonathan, Chou, Katherine J., Wu, Chao, Magnusson, Lauren R., Dong, Tao, and Maness, PinChing. Isotope-Assisted Metabolite Analysis Sheds Light on Central Carbon Metabolism of a Model Cellulolytic Bacterium Clostridium thermocellum. United States: N. p., Web. doi:10.3389/fmicb.2018.01947.
Xiong, Wei, Lo, Jonathan, Chou, Katherine J., Wu, Chao, Magnusson, Lauren R., Dong, Tao, & Maness, PinChing. Isotope-Assisted Metabolite Analysis Sheds Light on Central Carbon Metabolism of a Model Cellulolytic Bacterium Clostridium thermocellum. United States. doi:10.3389/fmicb.2018.01947.
Xiong, Wei, Lo, Jonathan, Chou, Katherine J., Wu, Chao, Magnusson, Lauren R., Dong, Tao, and Maness, PinChing. 2018. "Isotope-Assisted Metabolite Analysis Sheds Light on Central Carbon Metabolism of a Model Cellulolytic Bacterium Clostridium thermocellum". United States. doi:10.3389/fmicb.2018.01947. https://www.osti.gov/servlets/purl/1471551.
@article{osti_1471551,
title = {Isotope-Assisted Metabolite Analysis Sheds Light on Central Carbon Metabolism of a Model Cellulolytic Bacterium Clostridium thermocellum},
author = {Xiong, Wei and Lo, Jonathan and Chou, Katherine J. and Wu, Chao and Magnusson, Lauren R. and Dong, Tao and Maness, PinChing},
abstractNote = {Cellulolytic bacteria have the potential to perform lignocellulose hydrolysis and fermentation simultaneously. The metabolic pathways of these bacteria, therefore, require more comprehensive and quantitative understanding. Using isotope tracer, gas chromatography-mass spectrometry, and metabolic flux modeling, we decipher the metabolic network of Clostridium thermocellum, a model cellulolytic bacterium which represents as an attractive platform for conversion of lignocellulose to dedicated products. We uncover that the Embden-Meyerhof-Parnas (EMP) pathway is the predominant glycolytic route whereas the Entner-Doudoroff (ED) pathway and oxidative pentose phosphate pathway are inactive. We also observe that C. thermocellum's TCA cycle is initiated by both Si- and Re-citrate synthase, and it is disconnected between 2-oxoglutarate and oxaloacetate in the oxidative direction; C. thermocellum uses a citramalate shunt to synthesize isoleucine; and both the one-carbon pathway and the malate shunt are highly active in this bacterium. To gain a quantitative understanding, we further formulate a fluxome map to quantify the metabolic fluxes through central metabolic pathways. This work represents the first global in vivo investigation of the principal carbon metabolism of C. thermocellum. In conclusion, our results elucidate the unique structure of metabolic network in this cellulolytic bacterium and demonstrate the capability of isotope-assisted metabolite studies in understanding microbial metabolism of industrial interests.},
doi = {10.3389/fmicb.2018.01947},
journal = {Frontiers in Microbiology},
number = ,
volume = 9,
place = {United States},
year = {2018},
month = {8}
}

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