Sodium is required for nitrogenase activity in cyanobacteria

Abstract

The cyanobacteriaAnabaena torulosa andAnabaena L-31 require sodium (Na⁺) for growth on N₂ but not in the presence of NH₄ ⁺. Na⁺-starved cultures show relatively little or no nitrogenase activity although they differentiate normal heterocysts. Nitrogenase activity appears rapidly on addition of Na⁺ to Na⁺-starved cultures. The time course of appearance of activity after addition of Na⁺ suggests that Na⁺ is involved in activation of the existing enzyme rather than in its de novo synthesis.