Distinction between HCO3−- and CO2-dependent photosynthesis in the cyanobacterium Synechococcus leopoliensis based on the selective response of HCO3− transport to Na+

Abstract

AbstractAt low concentrations of dissolved inorganic carbon (DIC) at pH 8.0 the rates of DIC transport and fixation by Synechococcus leopoliensis were markedly stimulated by the addition of Na+ Carbonic anhydrase (CA) addition gave similar results. The Na+-stimulated photosynthesis was inhibited by Li+ whereas the CA-stimulated photosynthesis was not. The addition of a high DIC concentration (1 mM) overcame the need for either Na+ or CA. We suggest that Na+ stimulated HCO3− transport whereas CA stimulated CO2 transport (by increasing the supply rate of CO2 to the cells)