Psychrophilic and Psychrotolerant Yeasts

Cold habitats, defined by temperatures below 5 °C, cover much of the Earth and are vital for microbial diversity, particularly psychrophilic (cold-loving) and psychrotolerant (cold-tolerant) yeasts. These habitats, once thought lifeless, play key roles in biogeochemical cycles. Global warming has led to a steady reduction of these cold environments, spurring increased research into their microbial inhabitants. Studies have shifted from traditional culturing to more advanced methods like metagenomics, revealing a wider diversity of yeasts, both culturable and unculturable. Basidiomycota, especially genera like Cystobasidium, Mrakia, Vishniacozyma, Dioszegia, Glaciozyma, Naganishia, Saitozyma, Solicoccozyma, and Vanrija, dominate these ecosystems due to their efficient cold adaptations, such as polysaccharide capsule formation. Recent studies also suggest a greater diversity within Ascomycota such as Aureobasidium and Candida. Yeasts in these regions can be endemic or cosmopolitan, with some species showing psychrophilic behavior, while others exhibit psychrotolerant traits. Psychrophilic and psychrotolerant yeasts thrive in cold environments, adapting to harsh conditions like low temperatures, limited water availability, high ion concentrations, and UV radiation. These yeasts have developed several mechanisms to survive, including the synthesis of cold-active enzymes, antifreeze proteins, cryoprotectants, and extracellular polymers to prevent ice formation. Their membranes remain fluid at subzero temperatures due to increased unsaturated fatty acids. Genomic studies of Antarctic yeasts reveal genes that help them adapt to oxidative and cold stress. Cold-adapted yeasts have significant biotechnological potential, including the production of cold-active enzymes for industrial use, such as in food and detergent industries. They also produce antifreeze proteins with applications in cryopreservation and food preservation. These yeasts play crucial roles in bioremediation, biological pest control, and the production of biosurfactants. Despite the importance of cold habitats, they remain underexplored and vulnerable to climate change, highlighting the need for conservation and further research into these microorganisms.