INTRACELLULAR CONCENTRATION OF IONS IN A HALOPHILIC STRAIN OF CHLAMYDOMONAS. I. CONCENTRATION OF NA, K AND CL IN THE CELL

Metabolism and metabolomics of eukaryotes living under extreme conditions

Treatises on extremophiles are frequently focused on organisms belonging to the Archaea and Eubacteria kingdoms. However, a significant number of eukaryotes, both unicellular and multicellular, have evolved to live and thrive in extreme environments. Although less is known about eukaryotic life in extreme environments in comparison to prokaryotic extremophiles, advances in genomics and in comprehensive, high-throughput metabolic profiling techniques have provided new insight into the metabolic adaptations of eukaryotes living under extreme conditions. In this review, we will provide an overview of extremophilic life forms with emphasis on eukaryotes and we will compare metabolic adaptations in different eukaryotic extremophiles to identify generalities and specializations in adaptation to life under extreme conditions. Special emphasis will be devoted to the thermoacidophilic unicellular red alga Galdieria sulphuraria (Cyanidiaceae) as one example of a eukaryotic extremophile.

Ion metabolism in a halophilic blue-green alga, Aphanothece halophytica

The intracellular ion content of the halophilic blue-green alga, Aphanthece halophytica was studied as a function of age, external sodium and external potassium concentration. Intracellular Na+ was found to be about 0.38 millimoles/g dry mass. Intracellular K+ concentrations were as high as 1 M and varied directly with external salinity. Intracellular Ca++ and Mg++ were in the range previously reported for fresh water blue-green algae despite their extremely high extracellular concentrations. Average cell size is consistent at room temperature with two exceptions. When the outside K+ is lower than 6.5 mM the cells tend to be smaller with less intracellular K+ and high Ca++. In stationary phase cultrues the cells are larger with high intracellular Mg++ and low K+.