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Metabolic flux analysis of Cyanothece sp ATCC 51142 under mixotrophic conditions

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Title Metabolic flux analysis of Cyanothece sp ATCC 51142 under mixotrophic conditions
 
Creator ALAGESAN, S
GAUDANA, SB
SINHA, A
WANGIKAR, PP
 
Subject Cyanobacteria
Carbon labeling experiments
Glycerol
Diazotroph
Central carbon metabolism
BIDIRECTIONAL REACTION STEPS
ISOTOPE LABELING EXPERIMENTS
DIAZOTROPHIC CYANOBACTERIUM
CONTINUOUS-LIGHT
HYDROGEN-PRODUCTION
NETWORKS
GLUCOSE
GROWTH
MS
 
Description Cyanobacteria are a group of photosynthetic prokaryotes capable of utilizing solar energy to fix atmospheric carbon dioxide to biomass. Despite several "proof of principle" studies, low product yield is an impediment in commercialization of cyanobacteria-derived biofuels. Estimation of intracellular reaction rates by C-13 metabolic flux analysis (C-13-MFA) would be a step toward enhancing biofuel yield via metabolic engineering. We report C-13-MFA for Cyanothece sp. ATCC 51142, a unicellular nitrogen-fixing cyanobacterium, known for enhanced hydrogen yield under mixotrophic conditions. Rates of reactions in the central carbon metabolism under nitrogen-fixing and -non-fixing conditions were estimated by monitoring the competitive incorporation of C-12 and C-13 from unlabeled CO2 and uniformly labeled glycerol, respectively, into terminal metabolites such as amino acids. The observed labeling patterns suggest mixotrophic growth under both the conditions, with a larger fraction of unlabeled carbon in nitrate-sufficient cultures asserting a greater contribution of carbon fixation by photosynthesis and an anaplerotic pathway. Indeed, flux analysis complements the higher growth observed under nitrate-sufficient conditions. On the other hand, the flux through the oxidative pentose phosphate pathway and tricarboxylic acid cycle was greater in nitrate-deficient conditions, possibly to supply the precursors and reducing equivalents needed for nitrogen fixation. In addition, an enhanced flux through fructose-6-phosphate phosphoketolase possibly suggests the organism's preferred mode under nitrogen-fixing conditions. The C-13-MFA results complement the reported predictions by flux balance analysis and provide quantitative insight into the organism's distinct metabolic features under nitrogen-fixing and -non-fixing conditions.
 
Publisher SPRINGER
 
Date 2014-10-17T05:48:07Z
2014-10-17T05:48:07Z
2013
 
Type Article
 
Identifier PHOTOSYNTHESIS RESEARCH, 118(1-2)191-198
0166-8595
1573-5079
http://dx.doi.org/10.1007/s11120-013-9911-5
http://dspace.library.iitb.ac.in/jspui/handle/100/16106
 
Language en