EFFECT OF A SALT-OSMOTIC UPSHOCK ON THE EDAPHIC MICROALGA NEOCHLORIS-OLEOABUNDANS

The edaphic microalga Neochloris oleoabundans (isolated from desert soil) was subjected to a salt-osmotic shock from 0 to 0.6 kmol m-3 NaCl. The effect of the osmotic upshock on the cell composition was determined. The cell dry weight and the lipid, glycerol and soluble amino acids contents remained unchanged during 5d of osmotic upshock. The protein content increased after 2 d of initial osmotic shock, and it appears to be a long-term haloadaptation process of the cells. The most important short-term effects of salt osmotic upshock were a decrease in polysaccharide content and an increase in the soluble carbohydrate content of Neochloris oleoabundans cells. Within the first 4h after the initial shock, there was a transfer of carbon units from polysaccharides to sucrose which was independent of photosynthesis. The increase of intracellular concentration of sucrose contributed to cell osmoregulation.