Energy crosstalk between photosynthesis and the algal CO-concentrating mechanisms.

Microalgal photosynthesis is responsible for nearly half of the CO annually captured by Earth's ecosystems. In aquatic environments where the CO availability is low, the CO-fixing efficiency of microalgae greatly relies on mechanisms - called COconcentrating mechanisms (CCMs) - for concentrating CO at the catalytic site of the CO-fixing enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). While the transport of inorganic carbon (C) across membrane bilayers against a concentration gradient consumes part of the chemical energy generated by photosynthesis, the bioenergetics and cellular mechanisms involved are only beginning to be elucidated. Here, we review the current knowledge relating to the energy requirement of CCMs in the light of recent advances in photosynthesis regulatory mechanisms and the spatial organization of CCM components.