Naganishia friedmannii as viewed under a microscope.
Image Credit: Lara Vimercati.

Naganishia friedmannii is an extremely stress tolerant basidiomycete yeast that has been proposed as a model organism for exobiology and studies on stress resistance in eukaryotes^[1,2]. This yeast is very abundant in some of the most extreme environments of the Earth’s cryosphere^[3] and its survival limits have been investigated in a number of studies demonstrating its high tolerance of UV-B and UV-C radiation, extreme temperature fluctuations, desiccation and exposure to the stratosphere^[1,2,4]. This polyextremophilic yeast is the most abundant microeukaryote of high elevation volcanoes of the Atacama region and has been successfully isolated and cultured from soils collected from > 5000 m elevation on Volcán Llullaillaco, Chile.  Phylogenetic placement showed that the isolated strain is most closely related to members that have been found only at high altitude or high latitude^[2]. Experiments determined that its temperature optimum for growth is about 17°C and that it cannot grow at a constant temperature of 27°C. It can, therefore, be classified as a psychrotroph rather than a true psychrophile. Being a psychrotroph makes sense for an organism that experiences extreme temperature fluctuations in the environment. Further studies have shown that N. friedmannii can grow relatively rapidly in pure culture during freeze–thaw cycles^[2] and that it increases in relative abundance in soils subjected to freeze–thaw cycles both in its natural environment and in laboratory when water and nutrients are available^[5]. Furthermore, physiological experiments showed that this organism is metabolically versatile^[1] and can take advantage of stochastic inputs of carbon and nutrients from aeolian deposition.

References:

1. Pulschen AA, Rodrigues F, Duarte RT, Araujo GG, Santiago IF, Paulino-Lima IG, Rosa CA, Kato MJ, Pellizari VH, Galante D. UV-resistant yeasts isolated from a high-altitude volcanic area on the Atacama Desert as eukaryotic models for astrobiology. Microbiologyopen. 2015 Aug;4(4):574-88. doi: 10.1002/mbo3.262.
2. Vimercati L, Hamsher S, Schubert Z, Schmidt SK. Growth of high-elevation Cryptococcus sp. during extreme freeze-thaw cycles. Extremophiles. 2016 Sep;20(5):579-88. doi: 10.1007/s00792-016-0844-8.
3. Buzzini P, Branda E, Goretti M, Turchetti B. Psychrophilic yeasts from worldwide glacial habitats: diversity, adaptation strategies and biotechnological potential. FEMS Microbiol Ecol. 2012 Nov;82(2):217-41. doi: 10.1111/j.1574-6941.2012.01348.x.
4. Pulschen AA, de Araujo GG, de Carvalho ACSR, Cerini MF, Fonseca LM, Galante D, Rodrigues F. Survival of Extremophilic Yeasts in the Stratospheric Environment during Balloon Flights and in Laboratory Simulations. Appl Environ Microbiol. 2018 Nov 15;84(23):e01942-18. doi: 10.1128/AEM.01942-18.
5. Vimercati L, Bueno de Mesquita CP, Schmidt SK. Limited Response of Indigenous Microbes to Water and Nutrient Pulses in High-Elevation Atacama Soils: Implications for the Cold-Dry Limits of Life on Earth. Microorganisms. 2020 Jul 16;8(7):1061. doi: 10.3390/microorganisms8071061.