Cell cycle modeling of microalgae grown under a light-dark signal

Microalgae are photosynthetic microorganisms of growing industrial importance. Under natural illumination, they synchronize on the light signal, generating thus complex dynamics. A new model is proposed to represent the cell cycle dynamics of cells submitted to a light-dark signal. The model is based on a Droop approach relating the growth rate (in terms of carbon uptake) with the nitrogen status of the cell. Three main states are considered within the cell cycle: G1, G2 and M. The transition rate from one state to another is assumed to depend on the nutrient status (from G1 to G2) or on the light dose (from G2 to M). The model is then calibrated with experiments performed in various conditions of light and nitrogen supply. The model turns out to accurately represent the cell cycle dynamics, and the carbon fluxes. The model is successfully validated with data which were not used to set-up or calibrate the model.