CO2 concentrating mechanisms in photosynthetic microorganisms

Many microorganisms possess inducible mechanisms that concentrate CO2 at th e carboxylation site, compensating for the relatively low affinity of Rubis co for its substrate, and allowing acclimation to a wide range of CO2 conce ntrations. The organization of the carboxysomes in prokaryotes and of the p yrenoids in eukaryotes, and the presence of membrane mechanisms for inorgan ic carbon (Ci) transport, are central to the concentrating mechanism. The p resence of multiple Ci transporting systems in cyanobacteria has been indic ated. Certain genes involved in structural organization, Ci transport and t he energization of the latter have been identified. Massive Ci fluxes assoc iated with the CO2-concentrating mechanism have wide-reaching ecological an d geochemical implications.