Induction of Ferric Reductase Activity and of Iron Uptake Capacity in Chlorococcum littorale Cells under Extremely High-CO2 and Iron-Deficient Conditions

The marine green alga, Chlorococcum littorale, accumulated iron in its cells and showed high activity of plasma membrane ferric reductase under high-CO2 and iron-deficient conditions. These activities disappeared upon exposure to ordinary air and by adding excess FeSO4. The iron uptake had high affinity for the Fe(II) form (Km of 0.13 μM). Carbonylcyanide m-chlorophenylhydrazone and N,N-dicyclohexylcarbodiimide significantly suppressed the iron uptake, suggesting that the Fe(II) uptake was driven by ATPase. These results indicate that high CO2 and iron deficiency cooperatively induce the Fe(II) uptake and cell-surface ferric reductase activity.