Summary
Different techniques were investigated in order to determine the Na, K and Cl concentrations ofDunaliella tertiolecta cells adapted to a large range of salinity (20 to 1640 mM NaCl). The K cell concentrations were 6 to 13 times higher than the K concentration of the external medium (11 mM). The The Na and Cl cell concentrations, on the other hand, were lower than in the external medium at all salinities tested. Considerable differences in the absolute values of Na and Cl were, however, found according to the technique employed. These results are interpreted in terms of compartmentalization of the cells (at least two compartments). It is postulated that the larger compartment regulates its ion concentrations, maintaining low Na and Cl and high K concentrations, whereas the second compartment equilibrates with the external medium. The cation permeability of the membrane limiting the regulating compartment is altered by the antibiotics nystatin and monensin. Incubation of cells in K-free medium leads to a decrease of K and to an increase of the cell Na, this effect being reversed by addition of KCl to the medium. A good correlation is found between gain of K and loss of Na, suggesting a stoichiometric exchange of these two ions. The magnitude of this apparent Na/K exchange increases as the salinity increases. The external K concentration necessary to mediate half-saturation of the Na/K exchange is a function of the NaCl concentration of the adaptation medium. This Na/K exchange is partially light-dependant and inhibited by cold, cyanide and DCCD. It is suggested that this mechanism helps in the regulation of the ionic composition ofDunaliella cells.
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Ehrenfeld, J., Cousin, J.L. Ionic regulation of the unicellular green algadunaliella tertiolecta . J. Membrain Biol. 70, 47–57 (1982). https://doi.org/10.1007/BF01871588
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DOI: https://doi.org/10.1007/BF01871588