(590f) Contrasting the Metabolic Capabilities of Multiple Cyanobacterial Species

Cyanobacteria are an important group of photoautotrophic organisms that can synthesize valuable bioproducts by harnessing solar energy. Cyanobacteria contribute significantly to biological carbon sequestration, O₂ production and the nitrogen cycle. They exhibit robust growth under diverse environmental conditions and have minimal nutritional requirements. They are also endowed with high photosynthetic efficiencies and diverse metabolic capabilities that confer the ability to convert solar energy into a variety of biofuels and their precursors. However, less well studied are the similarities and differences that exist between the metabolic capabilities of different species of cyanobacteria that may contribute toward their niche biological functions. In this talk, we present progress in the development of genome-scale models of two phylogenetically close cyanobacterial species, namely Cyanothece 51142 (iRS703) and Synechocystis 6803 (iRS 661) to address these issues. Model iRS703 is comprised of 703 genes, 1654 reactions and 1837 metabolites; whereas model iRS661 spans 661 genes, 1693 reactions and 1896 metabolites. As many as 1484 reactions and 1705 metabolites are common in these two models. All reactions are elementally and charged balanced and localized into three different intracellular compartments (i.e., cytoplasm, carboxysome and thylakoid lumen). GPR (gene-protein-reaction) associations are also established based on the functional annotation information and homology prediction and categorized into five major classes of monofunctional proteins, multifunctional proteins, isozymes, multimeric proteins and protein complexes. We describe results from performing flux balance analysis under different physiological conditions, (i.e., phototrophic, chemotrophic and mixotrophic) and explore their impact on metabolic capabilities such as biomass formation, nitrogen fixation and hydrogen yield of these two cyanobacterial species.