title: Metabolic switching of central carbon metabolism in response to nitrate: application to autofermentative hydrogen production in cyanobacteria.
abstract: 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.
authors.affiliation: Waksman Institute and Department of Chemistry & Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA; Department of Chemistry, Princeton University, Princeton, NJ 08540, USA.
authors.forename: Kelsey
authors.initials: K
authors.lastname: McNeely
authors.affiliation: Waksman Institute and Department of Chemistry & Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA. Electronic address: kumargk@waksman.rutgers.edu.
authors.forename: G Kenchappa
authors.initials: GK
authors.lastname: Kumaraswamy
authors.affiliation: Waksman Institute and Department of Chemistry & Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA; Department of Chemistry, Princeton University, Princeton, NJ 08540, USA.
authors.forename: Tiago
authors.initials: T
authors.lastname: Guerra
authors.affiliation: Waksman Institute and Department of Chemistry & Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA; Department of Chemistry, Princeton University, Princeton, NJ 08540, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Bennette
authors.affiliation: Waksman Institute and Department of Chemistry & Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA.
authors.forename: Gennady
authors.initials: G
authors.lastname: Ananyev
authors.affiliation: Waksman Institute and Department of Chemistry & Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA. Electronic address: dismukes@rci.rutgers.edu.
authors.forename: G Charles
authors.initials: GC
authors.lastname: Dismukes
mesh_terms: D000693:Anaerobiosis; D002244:Carbon / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry / Q000378:metabolism; D005285:Fermentation; D006019:Glycolysis; D006859:Hydrogen / Q000032:analysis / Q000378:metabolism*; D042541:Intracellular Space / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D046940:Synechococcus / Q000378:metabolism*
chemical_list: D003470:Culture Media; D009566:Nitrates; D009573:Nitrites; D009243:NAD; D009249:NADP; D002244:Carbon; D006859:Hydrogen
keywords: Cyanobacteria; Fermentation metabolism; Glycolysis; Hydrogen; OPP