Coccomyxa subellipsoidea C-169, is unicellular green alga adapted to an extremely difficult Antarctic environment. It is a psychrotolerant (with optimum growth temperature 20°C) characterized by a wide range of temperature tolerances (up to + 30°C) and high lipid content. As the first sequenced eukaryotic microorganism from polar environment, it can serve as an attractive model for studies of the acclimatization to different temperatures and finally adaptation mechanisms to cold (Blanc et al., 2012).
This work aims to clarify the acclimatisation mechanisms that enable the psychrotolerant green alga C-169 to grow in a broad temperature spectrum. The contents of various biochemical compounds in cells, the lipid composition of the biological membranes of entire cells, and the thylakoid fraction as well as the electron transport rate and PSII efficiency were shown. The results demonstrate an acclimatization mechanism that is specific for C. subellipsoidea and that allows the maintenance of appropriate membrane fluidity, for example, in thylakoid membranes. It is achieved almost exclusively by changes within the unsaturated fatty acid pool, like changes from C18:2 into C18:3 and C16:2 into C16:3 or vice versa. This ensures, for example, an effective transport rate through PSII and in consequence a maximum quantum yield of it in cells growing at different temperatures. These findings add substantially to our understanding of the acclimatization of psychrotolerant organisms to a wide range of temperatures and prove that this process could be accomplished in a species-specific manner.
This work was supported by National Science Centre grant 2021/41/N/NZ3/04319.