Osmoregulation in Acanthamoeba castellanii—I. Variations of the concentrations of free intracellular amino acids and of the water content

Abstract

1. 1. The osmoregulation of Acanthamoeba castellanii, Neff strain, was studied in media having the same osmotic pressures but different salt contents. 2. 2. The amoeba survives a direct transfer from Neff's optimum growth medium, at 240 mOsmoles, to incubation media at 40, 200 and 500 mOsmoles. 3. 3. The amoeba water content is inversely proportional to the osmotic pressure of the incubation medium, but it is significantly influenced by the nature of the medium. 4. 4. The results of chromatographic analysis show that the free amino acid pool plays an active role in intracellular osmotic regulation. 5. 5. By comparing the results obtained in media having the same osmotic pressure but different salt contents, it is shown that the stimulus for increasing the concentration of free amino acids is mainly the osmolality of the medium. 6. 6. The role of the free amino acids in the osmoregulation of A. castellanii is discussed from the standpoint of comparative physiology.