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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nitrate removal from culture media is widely used to enhance autofermentative hydrogen production in cyanobacteria during dark anaerobiosis. Here we have performed a systematic inventory of carbon and nitrogen metabolites, redox pools, and excreted product fluxes which show that addition of nitrate to cultures of Synechococcus sp. PCC 7002 has no influence on glycogen catabolic rate, but shifts the distribution of excreted products from predominantly lactate and H2 to predominantly CO2 and nitrite, while increasing the total consumption of intracellular reducing equivalents (mainly glycogen) by 3-fold. Together with LC-MS derived metabolite pool sizes these data show that glycogen catabolism is redirected from the upper-glycolytic (EMP) pathway to the oxidative pentose phosphate (OPP) pathway upon nitrate addition. This metabolic switch in carbon catabolism is shown to temporally correlate with the pyridine nucleotide redox-poise (NAD(P)H/NAD(P)(+)) and demonstrates the reductant availability controls H2 evolution in cyanobacteria.
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PMID:Metabolic switching of central carbon metabolism in response to nitrate: application to autofermentative hydrogen production in cyanobacteria. 2475 36

Polyhydroxybutyrate (PHB) is a polymer of great interest as a substitute for conventional plastics, which are becoming an enormous environmental problem. PHB can be produced directly from CO2 in photoautotrophic cyanobacteria. The model cyanobacterium Synechocystis sp. PCC 6803 produces PHB under conditions of nitrogen starvation. However, it is so far unclear which metabolic pathways provide the precursor molecules for PHB synthesis during nitrogen starvation. In this study, we investigated if PHB could be derived from the main intracellular carbon pool, glycogen. A mutant of the major glycogen phosphorylase, GlgP2 (slr1367 product), was almost completely impaired in PHB synthesis. Conversely, in the absence of glycogen synthase GlgA1 (sll0945 product), cells not only produced less PHB, but were also impaired in acclimation to nitrogen depletion. To analyze the role of the various carbon catabolic pathways (EMP, ED and OPP pathways) for PHB production, mutants of key enzymes of these pathways were analyzed, showing different impact on PHB synthesis. Together, this study clearly indicates that PHB in glycogen-producing Synechocystis sp. PCC 6803 cells is produced from this carbon-pool during nitrogen starvation periods. This knowledge can be used for metabolic engineering to get closer to the overall goal of a sustainable, carbon-neutral bioplastic production.
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PMID:PHB is Produced from Glycogen Turn-over during Nitrogen Starvation in Synechocystis sp. PCC 6803. 3101 17