title: Network identification and flux quantification of glucose metabolism in Rhodobacter sphaeroides under photoheterotrophic H(2)-producing conditions.
abstract: The nonsulfur purple bacteria that exhibit unusual metabolic versatility can produce hydrogen gas (H(2)) using the electrons derived from metabolism of organic compounds during photoheterotrophic growth. Here, based on (13)C tracer experiments, we identified the network of glucose metabolism and quantified intracellular carbon fluxes in Rhodobacter sphaeroides KD131 grown under H(2)-producing conditions. Moreover, we investigated how the intracellular fluxes in R. sphaeroides responded to knockout mutations in hydrogenase and poly-β-hydroxybutyrate synthase genes, which led to increased H(2) yield. The relative contribution of the Entner-Doudoroff pathway and Calvin-Benson-Bassham cycle to glucose metabolism differed significantly in hydrogenase-deficient mutants, and this flux change contributed to the increased formation of the redox equivalent NADH. Disruption of hydrogenase and poly-β-hydroxybutyrate synthase resulted in a significantly increased flux through the phosphoenolpyruvate carboxykinase and a reduced flux through the malic enzyme. A remarkable increase in the flux through the tricarboxylic acid cycle, a major NADH producer, was observed for the mutant strains. The in vivo regulation of the tricarboxylic acid cycle flux in photoheterotrophic R. sphaeroides was discussed based on the measurements of in vitro enzyme activities and intracellular concentrations of NADH and NAD(+). Overall, our results provide quantitative insights into how photoheterotrophic cells manipulate the metabolic network and redistribute intracellular fluxes to generate more electrons for increased H(2) production.
authors: Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
authors: Yongzhen
authors: Y
authors: Tao
authors: Deng
authors: D
authors: Liu
authors: Xing
authors: X
authors: Yan
authors: Zhihua
authors: Z
authors: Zhou
authors: Jeong K
authors: JK
authors: Lee
authors: Chen
authors: C
authors: Yang
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D002244:Carbon / Q000378:metabolism; D002247:Carbon Isotopes; D008401:Gas Chromatography-Mass Spectrometry; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D005947:Glucose / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism*; D008027:Light; D053858:Metabolic Networks and Pathways / Q000502:physiology; D009243:NAD; D009584:Nitrogen / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D012242:Rhodobacter sphaeroides / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D000596:Amino Acids; D002247:Carbon Isotopes; D009243:NAD; D018698:Glutamic Acid; D002244:Carbon; D006859:Hydrogen; D010088:Oxidoreductases; C029746:uptake hydrogenase; D005947:Glucose; D009584:Nitrogen; D005990:Glycerol