Sack Lunch Seminar (SLS)

We present a new, steady-state macromolecule-based model to study light-nutrient co-limitation of phytoplankton growth. The model is based on simplified metabolic flux network and resolves key pools of macro-molecules, each of which has different roles for cellular growth. The model is used to predict and interpret the variation of cellular stoichiometry of fresh water Synechococcus sp. under different light and nutrient environment over a range of dilution rates (averaged growth rates) in a steady state culture. The model explains the different response of cellular nitrogen and phosphorus quota to the various light-nutrient environments, predicting protein and RNA as most influential molecules on nitrogen and phosphorus quotas respectively. The model indicates that, though total nitrogen storage is larger than phosphorus storage, relative to requirements, many times more phosphorus can be stored. It accurately predicts the maximum possible growth rate based on the limits of resource allocation within the cell. Finally, the model predicts nutrient-light co-limitation of cell population density under different dilution rates. While the nutrient has a direct effect on the population density, light impacts it by modifying the cellular stoichiometry. This steady-state, macromolecule based model provides bases for predicting phytoplankton growth in different dynamic environments