Effect of acetazolamide on stable carbon isotope fractionation in Chlamydomonas reinhardtii and Chlorella vulgaris

The effect of extracellular carbonic anhydrase (CAex) on stable carbon isotope fractionation in algae is still unclear. The stable carbon isotope composition and algal growth in the presence and absence of the membrane-impermeable CA inhibitor acetazolamide were compared in Chlamydomonas reinhardtii and Chlorella vulgaris. The CAex of both algal species contributed about 9‰ of the stable carbon isotope fractionation and exhibited a dosage effect. Therefore, evidence in vivo that CAex leads to a larger carbon isotope fractionation of algae is presented.