(773d) Metabolic Model of Trichodesmium Erythraeum, a Marine Diazotroph

It is estimated that 42% of the annual global nitrogen fixation is performed by the marine cyanobacterium, Trichodesmium. It is also known to leak 30 â?? 50 % of the nitrogen it fixes, thus acting as an important source of biologically available nitrogen in the open ocean. Trichodesmium is a unique diazotrophic cyanobacterium because it can simultaneously fix carbon and nitrogen by differentiating the metabolic pathways in two subsets of cells while maintaining similar cellular structure. Despite the prominence of this organism in the nitrogen cycle, little work has been done to investigate how carbon and nitrogen is directed through metabolism within and between cells. We have reconstructed the metabolic network of T. erythraeum, which is the one species of Trichodesmium with a sequenced genome. We have used this model to predict fluxes between cells based on constraints which we have measured in the lab or in situ data found in literature. Our model successfully predicts equilibrium cell compositions (carbon fixing versus nitrogen fixing) which have been measured in the open ocean. This model will be further refined and improved to enable more advanced modeling of cultures with distinct metabolisms.