Multiparameter-based photosynthetic state transitions of single phytoplankton cells

Abstract

Fluorescence emitted by light-harvesting pigments responds to the physiological state of phytoplankton. We developed a time resolved system to monitor fluorescence from single cells. It captures multiple spectral channels and fluorescence lifetimes, eliminating ensemble averaging of bulk experiments. Tracking the diurnal cycles of three phytoplankton species, we uncover each species segregation into multiple distinct cell states, a feature previously hidden in bulk measurements. We also tested their response to light-intensity perturbations, and determined each species unique acclimation strategy involving transition between distinct cell subpopulations. This approach will be useful for characterizing natural phytoplankton population responses to environmental conditions, aiming for a better understanding of their acclimation strategies and the effects of global climate changes.