# Cell Response to Oxidative Stress in Antarctic Filamentous Fungi
## 10 Concluding Remarks  
In recent years, survival in extreme cold temperatures has sparked growing interest in the biodiversity, ecology, and biotechnological potential of Antarctic microorganisms. Furthermore, they are the subject of exobiology as a unique model for evolutionary studies. Several scientists point out the similarity between the conditions of existence of microorganisms in some regions of Antarctica (e.g., deep ice, rock crevices, frozen soil, etc.) and those on the planet Mars. The Antarctic cold, arid climate, and remoteness from the rest of the Earth's surface are responsible for the preservation of many life forms untouched by human civilization. In addition, low temperatures, short summers, high concentrations of salts and UV radiation, and many other factors have a significant impact on the type of microorganisms that survive in this place. Despite the extremely negative effect of cold temperatures on biochemical reactions, Antarctic fungi grow at rates similar to those achieved by related species living in temperate climates. This tolerance in conditions of extremely low temperatures is related to the cellular response to oxidative stress induced by the available abiotic factors. Antarctic fungi demonstrate the formation of ROS even at an optimal growth temperature, which is adequate for their survival mechanisms. Lowering the temperature, however, causes accelerated generation of ROS, which leads to the realization of oxidative stress. Data on the induction of oxidative stress in Antarctic fungi after exposure to low temperatures and their response are very scarce. Even less studied are the fungi isolated from the area of the Bulgarian base \"St. Kliment Ohridski\" on Livingston Island. This review presents data on the biodiversity of filamentous fungi in the Antarctic region and their tolerance to low temperatures. As is clear from this review, cold stress causes significant oxidative damage to all cellular molecules in Antarctic fungi, such as lipids, proteins, and DNA. This results in substantial changes in the structure and fluidity of cell membranes, modifications to the structures of enzymes and other functional proteins, changes in the profile of bases in the DNA molecule, breakage of DNA chains, and numerous additional effects. In the course of their evolution, Antarctic fungi have developed efficient survival mechanisms in harsh conditions, specifically at extremely low temperatures. Their survival strategies encompass modifications in cell and colony morphology, such as melanoma, and the promotion of meristematic development. The literature documents significant ultrastructural changes, including an increase in vacuolar volume, focal damage to the cell wall, rupture of nuclear membranes, and structural changes in the mitochondria. The physiological adaptation of these organisms may encompass a variety of individual strategies or a synthesis of multiple approaches. Growth retardation, including a decrease in the amount of biomass, has been observed to occur as a result of the cold-shock-induced autolysis process. Furthermore, under cold stress conditions, it has been observed that the metabolic pathways of reserve carbohydrate synthesis and stress protectants trehalose and glycogen are triggered, resulting in their accumulation within the cells. Cold tolerance is facilitated by the presence of cold-active enzymes, which enhance metabolic activities, substrate assimilation, growth, and reproduction of these organisms. In this review, we have also focused on the antioxidant defense mechanisms employed by Antarctic fungi. They promptly identify and respond to the changes in the level of ROS by inducing protective enzymes that counteract oxidative damage (SOD, CAT, GPx) as well as non-enzyme antioxidants. A significant research direction pertains to the comparison of the cellular response to oxidative stress in strains isolated from Antarctica and those from temperate habitats. The acquisition of such data may contribute to the elucidation of the cold-adapted mechanism.