# Cell Response to Oxidative Stress in Antarctic Filamentous Fungi
## 7 Cold Stress Response of Antarctic Fungi and Adaptation
### Physiological Modification Caused by Cold Stress  
It is evident that to overcome any type of stress, including cold stress, changes in cell physiology are required, which subsequently result in positive selection [7]. Adaptation at the physiological level may involve individual strategies or a combination of them. One of the initial responses to a reduction in the growth temperature of microorganisms is a cessation of growth. This is followed by an acclimation phase, which is a period of latency preceding the restoration of cell growth [210]. During this phase, there is a transient inhibition of the synthesis of the majority of cellular proteins, most likely at the level of translation. A drastic effect of low temperatures on the growth of Antarctic fungal cultures was found in _Pseudogymoascus roseus_[190], _Mrakia bollopis_ SK-4 and TKG1-2 [50], and _P. griseofulcum_[171]. In addition, a decrease in biomass content has been documented in fungal strains isolated from soil samples in three areas of Antarctica: Casey Station, Terra Nova Bay, and South Georgia, due to both long-term and short-term exposure to low temperatures [38; 87; 170]. A comparative analysis of the cell response of Antarctic fungi to a reduction in temperature, focusing on two thermal classifications, psychrotolerant and mesophilic, indicated a complete cessation of growth or a marked reduction in biomass [163]. This effect was notably more significant in the mesophilic fungus than in the psychrophilic ones. A similar trend has been observed in the Antarctic strains _P. olsonii_ p14 and _P. waksmanii_ m12, as well as in the temperate strain _P. rugulosum_ t35, when exposed to the temperature downshift during the stationary growth phase [52]. The reduction in biomass, known as cold-shock-induced autolysis, is linked to the activation of genes that encode peptidoglycan hydrolases, which facilitate the process of autolysis [210]. Similar findings have been reported for various microorganisms exposed to cold stress, such as _Pichia pastoris_[189], _Volvariella volvacea_[191], etc. The phenomenon of low-temperature autolysis coincided with reduced glucose consumption [37; 52; 163; 171]. The findings presented by [PERSON] et al. [211] indicated that the low-temperature autolysis in _V. volvacea_ resulted from both intracellular and extracellular interactions. The authors proposed that the variations in metabolites and genes associated with malate metabolism played a role in supplying electrons to the electron transport chain. However, prolonged exposure to low temperatures led to an inadequate intracellular energy supply, ultimately resulting in cold-induced damage. The accumulation of trehalose and glycogen in microbial cells under adverse growth conditions can serve as indicators of stress [11; 212; 213; 214]. Trehalose is a vital storage compound found in both the vegetative cells and spores of fungi, and it is recognized as the most commonly occurring disaccharide among fungal species [6]. Its role as a universal stress protectant in the cytosol is significant, particularly in its ability to stabilize membranes during episodes of dehydration [214]. The stabilizing properties of trehalose can be attributed to the formation of a strong hydrogen bonding network that links biomolecules to the sugar-water matrix [215]. This connection inhibits the unfolding of biomolecules, as it involves a reconfiguration of the surrounding medium. Glycogen serves as the common carbohydrate storage and energy reservoir in fungi, especially during periods of stress. This polysaccharide consists of glucose units connected by \(\alpha\), 1-4 glycosidic bonds, with additional \(\alpha\), 1-6 branching points. The metabolism of glycogen is governed by a complex network of interactions involving numerous genes and biochemical pathways. Key to this metabolic process are five critical enzymes: ADP-glucose pyrophosphrolase (GlgC), glycogen synthase (GlgA), glycogen branching enzyme (GlgB), glycogen phosphorylase (GlgP), and glycogen debranching enzyme (GlgX) [216; 217].