title: Genome-scale modeling of light-driven reductant partitioning and carbon fluxes in diazotrophic unicellular cyanobacterium Cyanothece sp. ATCC 51142.
abstract: Genome-scale metabolic models have proven useful for answering fundamental questions about metabolic capabilities of a variety of microorganisms, as well as informing their metabolic engineering. However, only a few models are available for oxygenic photosynthetic microorganisms, particularly in cyanobacteria in which photosynthetic and respiratory electron transport chains (ETC) share components. We addressed the complexity of cyanobacterial ETC by developing a genome-scale model for the diazotrophic cyanobacterium, Cyanothece sp. ATCC 51142. The resulting metabolic reconstruction, iCce806, consists of 806 genes associated with 667 metabolic reactions and includes a detailed representation of the ETC and a biomass equation based on experimental measurements. Both computational and experimental approaches were used to investigate light-driven metabolism in Cyanothece sp. ATCC 51142, with a particular focus on reductant production and partitioning within the ETC. The simulation results suggest that growth and metabolic flux distributions are substantially impacted by the relative amounts of light going into the individual photosystems. When growth is limited by the flux through photosystem I, terminal respiratory oxidases are predicted to be an important mechanism for removing excess reductant. Similarly, under photosystem II flux limitation, excess electron carriers must be removed via cyclic electron transport. Furthermore, in silico calculations were in good quantitative agreement with the measured growth rates whereas predictions of reaction usage were qualitatively consistent with protein and mRNA expression data, which we used to further improve the resolution of intracellular flux values.
authors.affiliation: Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Trang T
authors.initials: TT
authors.lastname: Vu
authors.forename: Sergey M
authors.initials: SM
authors.lastname: Stolyar
authors.forename: Grigoriy E
authors.initials: GE
authors.lastname: Pinchuk
authors.forename: Eric A
authors.initials: EA
authors.lastname: Hill
authors.forename: Leo A
authors.initials: LA
authors.lastname: Kucek
authors.forename: Roslyn N
authors.initials: RN
authors.lastname: Brown
authors.forename: Mary S
authors.initials: MS
authors.lastname: Lipton
authors.forename: Andrei
authors.initials: A
authors.lastname: Osterman
authors.forename: Jim K
authors.initials: JK
authors.lastname: Fredrickson
authors.forename: Allan E
authors.initials: AE
authors.lastname: Konopka
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Beliaev
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Reed
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D057486:Carbon Cycle / Q000502:physiology* / Q000528:radiation effects; D003198:Computer Simulation; D046889:Cyanothece / Q000378:metabolism* / Q000528:radiation effects; D016678:Genome / Q000502:physiology*; D008027:Light; D008954:Models, Biological; D020543:Proteome / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology* / Q000528:radiation effects
chemical_list: D001426:Bacterial Proteins; D020543:Proteome