Current research is directed towards: identifying the molecular components essential to the CO2 - concentrating mechanism (CCM) of aquatic, photosynthetic microorganisms; defining the role of carbonic anhydrase in photosynthesis & the CCM; acquiring an understanding of the biochemical mechanisms involved in the active transport of CO2 and HCO3-; regulation of expression of the CO2/HCO3- transport systems and the control of photosynthetic electron transport by CO2/HCO3-. Using molecular and biochemical tools, we are analysing the structure, function,assembly and protein targeting to carboxysomes, the unique CO2 fixing compartment of cyanobacteria. We have recently discovered a novel evolutionary lineage of carbonic anhydrase (epsilon CA) resident in the carboxysomes of the dominant cyanobacteria from the open oceans that is essential for growth and photosynthesis. Studies with eukaryotic algae have identified a novel mitochondrial-driven HCO3- transport system that supports photosynthesis in a marine alga and this has sparked investigations into the interactions between mitochondria and chloroplasts during photosynthesis.