One main issue in aquatic systems, where most cyanobacteria live, is
the low availability of inorganic carbon (Ci), which is controlled by different
external parameters like pH, temperature, and gas-exchange.
[14]. The CO2 diffusion in air is faster than in water and consequently
the equilibrium between CO2 and HCO3
, in water, is relatively slow
for pHs between 7 and 8.5. Therefore, cyanobacteria have developed a
CO2-concentrating mechanism (CCM) in order to ensure that RuBisCO
is surrounded by CO2 and thereby avoid the oxygenase reaction [15].
Since the cyanobacterial RuBisCO has low affinity for CO2, these microorganisms
may not have survived in the aquatic habitat without a
CCM