Comparative lipidomics of snow algal blooms

Snow algae are excellent models for elucidating adaptations to abiotic stresses that characterize their extreme habitat. In cold-adapted microorganisms, changes in lipid composition represent an important strategy that enables survival at low temperatures. However, our knowledge in this field remains fragmentary. Using shotgun lipidomics, we identified 303 lipid species in field samples of snow algal blooms originating from 14 sites across a wide altitudinal gradient in mountains of Central Europe. Red, orange, and green snow blooms caused by vegetative cells or cysts of species from the genera Sanguina, Chloromonas, and Chlainomonas (Chlamydomonadales, Chlorophyta) were sampled. The analysis of total lipids using hydrophilic interaction chromatography showed that the samples were dominated by sphingolipids and triacylglycerols, forming 39.9–50.5% and 21.9–31.8% out of total lipids, respectively. Significant variability in lipid composition was revealed, reflecting differences in life cycle stage or metabolic setting and species composition among blooms of different color. Vegetative cells were characterized by a higher proportion of phospholipids (mean 18.0% vs. 13.5%. in orange and 14.4% in red cysts) and glycolipids (mean 17.3% vs. 13.2% and 10.3%), whereas triacylglycerols were less represented compared to the other two groups (mean 22.3% vs. 30.2% and 28.3%). This pattern was in line with the assumed physiological difference between the two main stages of the life cycle in chlamydomonadacean snow algae. A higher degree of unsaturation of phospholipid species in algal cells causing red blooms suggested a better adaptation of membranes to low temperatures compared to green and orange snow blooms.