Ion Content of the Halotolerant Alga Dunaliella salina

The intracellular concentration of the major ions in Dunaliella salina cells were determined, following the removal of extracellular ions by ion-exchange minicolumns. Log phase cells, grown in media containing 1–4 molar NaCl, contained 30–50 mM chloride and 200–350 mM magnesium (5 mM in medium). Phosphorus, which is present intracellularly mostly as polyphosphate, was present in amounts of 60–100 fmoles per cell, equivalent to a concentration of 600–1,000 mM (0.2 mM in medium). Previous data indicated that such cells contained 20–40 mM Na+, 150–300mM K+, 20mM SO2−4, and very low concentrations of Ca2+ and charged nitrogenous compounds. Mg2+ and K+ seem to serve as the major counter ions for the intracellular negative charge present in the massively accumulated polyphosphates. The former accounts for about 2/3 of the required positive charge. This is supported by the observation that limitation in the phosphate or K+ supply in the medium lead to a parallel decrease in the accumulation of intracellular phosphorus, Mg2+ or K+.