Lipid composition of Euglena gracilis in relation to carbon-nitrogen balance
1995
Regnault, A. | Chervin, D. | Chammal, A. | Piton, F. | Calvayrac, R. | Mazliak, P.
The lipid class and fatty acid compositions of Euglena gracilis were analysed after growth under various conditions of autotrophy or photoheterotrophy, in order to identify the contribution of lactate (a carbon source) and ammonium phosphate (a nitrogen source) to the metabolism of these compounds. When ammonium and lactate were both present in the medium, in concentrations that allowed growth, the lipid composition of algae appeared to be independent of the ammonium concentration. The effects of increasing ammonium phosphate concentration on lipid metabolism were observed only when lactate was depleted. With increasing nitrogen concentration in the medium, an increase in the content of galactolipids rich in polyunsaturated C16 and C18 fatty acids (FA) was noted, as well as an increase in the monogalactosyldiacylglycerol:digalactosyldiacylglycerol ratio; these changes could be related to an increase in the number of the stacked lamellae present in chloroplasts. Nitrogen concentration had no influence on the C12 and C14 FA but induced a loss of C22 FA. In the absence of ammonium phosphate in the culture medium, increasing lactate concentrations were accompanied by a decrease in all plastic lipids, whereas the content of storage lipids (enriched in 14:0 and 16:0) increased. Partial inhibition of the polydesaturation of C18 FA was observed and was accompanied by an accumulation of 18:1.
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