Studies on Lipid Changes During the Development of Frost Hardiness in Chlorella ellipsoidea

Abstract

Chlorella ellipsoidea cells at an intermediate stage in the ripening phase of the cell cycle were hardened at 3℃ for 48 hr. Lipid changes during the development of frost hardiness were measured. Phospholipids and glycolipids increased from 0.4 μmoles to 1.2 μmoles/10^9 cells and from 0.9 μmoles to 1.6 μmoles/10^9 cells, respectively. The ratio of lipid (mg)/protein (mg) in hardened cells was about 1.4 times that in unhardened cells. These results suggest that the algal cells change into more lipid-enriched state during the development of frost hardiness and that considerable change in lipid metabolism is involved in the development of the algal hardiness. Moreover, the ratios of individual phospholipids to monogalactosyl diglyceride tended to increase during the hardening process. Non-polar lipid which remarkably increased with an increase in frost hardiness was detected. According to studies on inhibitory effect of oligomycin or 3-(3,4-dichlorophenyl)-1, 1-dimethylurea on the increase of frost hardiness, the non-polar lipid was always synthesized whenever the algal cells developed the frost hardiness. These results suggest the existence of an intimate correlation between the content of the non-polar lipid and frost hardiness and the importance of the non-polar lipid in lipid metabolism associated with the hardiness change in Chlorella