title: A Comprehensively Curated Genome-Scale Two-Cell Model for the Heterocystous Cyanobacterium Anabaena sp. PCC 7120.
abstract: Anabaena sp. PCC 7120 is a nitrogen-fixing filamentous cyanobacterium. Under nitrogen-limiting conditions, a fraction of the vegetative cells in each filament terminally differentiate to nongrowing heterocysts. Heterocysts are metabolically and structurally specialized to enable O2-sensitive nitrogen fixation. The functionality of the filament, as an association of vegetative cells and heterocysts, is postulated to depend on metabolic exchange of electrons, carbon, and fixed nitrogen. In this study, we compile and evaluate a comprehensive curated stoichiometric model of this two-cell system, with the objective function based on the growth of the filament under diazotrophic conditions. The predicted growth rate under nitrogen-replete and -deplete conditions, as well as the effect of external carbon and nitrogen sources, was thereafter verified. Furthermore, the model was utilized to comprehensively evaluate the optimality of putative metabolic exchange reactions between heterocysts and vegetative cells. The model suggested that optimal growth requires at least four exchange metabolites. Several combinations of exchange metabolites resulted in predicted growth rates that are higher than growth rates achieved by only considering exchange of metabolites previously suggested in the literature. The curated model of the metabolic network of Anabaena sp. PCC 7120 enhances our ability to understand the metabolic organization of multicellular cyanobacteria and provides a platform for further study and engineering of their metabolism.
authors.affiliation: Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom (D.M., P.R.J.); and.|Institute for Theoretical Biology, Humboldt University Berlin, 10115 Berlin, Germany (R.S.).
authors.forename: David
authors.identifier: 0000-0002-4155-2085
authors.initials: D
authors.lastname: Malatinszky
authors.affiliation: Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom (D.M., P.R.J.); and.|Institute for Theoretical Biology, Humboldt University Berlin, 10115 Berlin, Germany (R.S.).
authors.forename: Ralf
authors.initials: R
authors.lastname: Steuer
authors.affiliation: Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom (D.M., P.R.J.); and p.jones@imperial.ac.uk.|Institute for Theoretical Biology, Humboldt University Berlin, 10115 Berlin, Germany (R.S.) p.jones@imperial.ac.uk.
authors.forename: Patrik R
authors.identifier: 0000-0001-7618-8204
authors.initials: PR
authors.lastname: Jones
mesh_terms: D017033:Anabaena / Q000166:cytology* / Q000235:genetics* / Q000378:metabolism; D018533:Biomass; D002244:Carbon / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial; D008954:Models, Biological; D009586:Nitrogen Fixation
chemical_list: D002244:Carbon