Cyanobacteria have developed up to five different transporters to actively
acquire and transport inorganic carbon into the cells. Some transporters
are expressed constitutively while others are induced when
only limited levels of carbon are present [15] and [17]. In addition,
light is a pre-requisite for the expression of the genes encoding Ci uptake
transporters, and their transcription is dependent on cyclic photosynthetic
electron flow around photosystem I [18]. Cyanobacteria may
incorporate two different forms of Ci, CO2 and HCO3
−. In addition,
there are specific uptake systems; three for the import of HCO3
− and
two for the import of CO2