LIPID-COMPOSITION DURING GROWTH OF MOTILE AND COCCOLITH FORMS OF EMILIANIA-HUXLEYI

Flagellated and coccolith cell types of Emiliania huxleyi were grown a xenically and the lipid class and fatty acid compositions of the main polar lipid classes examined throughout the growth cycle. The lipid co mpositions of the two cell types were similar with only slight differe nces noted, the coccolith form tending to have higher levels of neutra l lipids than the flagellate. Methyl and ethyl ketones were present in both cell types. The proportion of phospholipids and glycolipids incr eased during the log-phase, while neutral lipids (free fatty acids, tr iacylglycerois, ketones and hydrocarbons) achieved their highest level s in the late stationary-phase. The polar lipids of both cell types we re very rich in polyunsaturated fatty acids (PUFA). In sulphoquinovosy lglyercol + phosphatidylethanolamine, 18:3n-3 and 18:4n-3 were the pre dominant fatty acids totalling 42.4-55.7%, while 18:5n-3 (33.1-79.2%) was the main fatty acid in digalactosyldiacylglycerols. This fatty aci d was also predominant in monogalactosydiacylglycerols (36.6-57.7%), w ith lesser amounts of 18:4n-3 and 22:6n-3. Phosphatidylcholine was dom inated by two molecular species, 22:6n-3/22:6n-3 and 14:0/22:6n-3, acc ounting for 25.7-33.7 and 42.0-58.3%, respectively. Changes in PUFA co mposition over the growth cycle were small. The C-18 PUFA associated w ith thylakoid glycolipids tended to increase during the log-phase and decreased in the late stationary-phase while 22:6n-3 peaked in the lat e stationary-phase. The results are discussed in relation to the ecolo gy of this alga.