Dynamics of fluxes through photosynthetic complexes in response to changing light and inorganic carbon acclimation in Synechococcus elongatus.

Cyanobacteria acclimate to environmental inorganic carbon (C(i)) concentrations through re-organisations of photosynthetic function and the induction of carbon concentrating mechanisms (CCMs), which alter and constrain their subsequent acclimation to changing light. We grew cells acclimated to high C(i) (4 mM) or low C(i) (0.02 mM), shifted them from 50 micromol m(-2) s(-1) to 500 micromol m(-2) s(-1), and quantified their photosynthetic performance in parallel with quantitation of allocations to key indicator macromolecules.

Large reallocations of carbon, nitrogen, and photosynthetic reductant among phycobilisomes, photosystems, and Rubisco during light acclimation in Synechococcus elongatus strain PCC7942 are constrained in cells under low environmental inorganic carbon.

Synechococcus elongatus strain PCC7942 cells were grown in high or low environmental concentrations of inorganic C (high-C(i), low-C(i)) and subjected to a light shift from 50 micromol m(-2) s(-1) to 500 micromol m(-2) s(-1). We quantified photosynthetic reductant (O(2) evolution) and molar cellular contents of phycobilisomes, PSII, PSI, and ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco) through the light shift. Upon the increase in light, small initial relative decreases in phycobilisomes per cell resulted from near cessation of phycobilisome synthesis and their dilution into daughter cells.