A Reaction-Diffusion Frame for Accessing Metabolic O Fluxes in Single Microalgal Cells with Low-Cost Wide-Field Imaging of Nanosensor Luminescence Lifetime.

In cells, many small molecules are membrane-permeant. This feature opens a road to analyze their flux of production or consumption by quantitatively interpreting the map of their extracellular concentration within a reaction-diffusion frame. Here, this approach is implemented with a new wide-field lifetime imaging protocol applied to single microalgae cells sparsely deposited on an agarose pad loaded with a luminescent dioxygen (O) nanosensor. The resulting maps are processed to access the spatial distribution of the O concentration in the plane of the cells. After fitting the data, the cellular O flux is extracted, evidencing a span of magnitudes and angular dependencies in the balance between photosynthesis and respiration. Beyond pointing to the disparity of individual behavior within the same colony, this work validates a simple approach for characterizing metabolic fluxes of membrane-permeant molecules down to the single-cell level.