Inter-strain variability in the photosynthetic use of inorganic carbon, exemplified by the pH compensation point, in the cyanobacterium Microcystis aeruginosa

Inter-strain variability in pH compensation point (pHc) in the cyanobacterium Microcystis aeruginosa has been investigated. The pHc allows one to discriminate whether the organism is able to take up HCO3− as inorganic carbon (Ci) source in photosynthesis. Eight subgroups were found according to the pHc value, ranging from 10.44 ± 0.22 to 11.67 ± 0.05. The high variability in pHc (and consequently, in the capacity to use HCO3− as Ci source) suggested that different HCO3− use mechanisms could occur in M. aeruginosa and, from an evolutionary point of view, this trait is not under high natural selective pressure.