Dynamic response of Synechocystis sp PCC 6803 to changes in light intensity

With changing light intensities, microalgae exhibit the inter-connected phenomena of photoacclimation, photodamage, and photodamage repair. Together they result in unique growth responses to changes in light intensity. In this work, we experimentally evaluated the growth responses using Synechocystis sp. PCC 6803 subjected to a series of light-step experiments. In these experiments, the biomass density and average light intensity were held constant (after the step in light intensity), and the dynamic response of the specific growth rate was measured. The over-arching trend is that an increasing-light step gave a rapid spike in growth rate, followed by a depression and ultimately restabilization of the growth rate for the new light condition. A decreasing-light step led to a small depression in growth rate before a gradual restabilization for the new light condition. Photoacclimation was faster after an increasing-light step than a decreasing-light step. Using a model accounting for photoacclimation, photodamage, and photodamage repair (presented in a companion paper), we captured the dynamic growth response and explained how the responses were the result of the combined effects of light absorption, photoacclimation, and photodamage.