Cold adaptation mechanisms of the psychrotolerant filamentous ascomycete Psychrophilomyces antarcticus.

To adapt to cold environments, such as the Arctic and Antarctic regions, high mountain peaks, cold soils, deserts, caverns, and cryopegs, fungi employ various strategies. Crucial aspect of this adaptation is maintaining the functions of their cell membranes. To study the mechanisms of cell membrane protection, we analyzed the composition of osmolytes and membrane lipids and their fatty acids in a submerged culture of the psychrotolerant fungus Psychrophilomyces antarcticus during growth at temperatures of 20 °C and 8 °C. The object of the study exhibits a broad growth range from - 3 °C to 27 °C, with an optimal temperature of 20-22.5 °C. For adaptation to cold (8 °C), the fungus significantly increases the degree of unsaturation of phospholipids by enhancing the proportion of α-linolenic acid (40% of the total), compared to the optimal temperature (15% of the total). Additionally, the proportion of sterols in the membrane lipids is twice as low, and the amount of arabitol in the composition of osmolytes is twice as high, compared to the optimal temperature. At both temperatures, the fungus is characterized by the dominance of two osmolytes in the cytosol: trehalose and arabitol. It also shows a predominance of non-bilayer phospholipids, specifically phosphatidic acids (35-42% of the total) and phosphatidylethanolamines (~ 20% of the total), in its membrane lipid composition, along with trace amounts of sterol esters and the formation of mucus in the culture fluid. The combined adjustments in osmolyte and membrane lipid profiles contribute to the fungus' adaptation to a wide range of temperatures. These findings provide insights into the molecular basis of psychrotolerance and open up opportunities for research into potential biotechnological applications.