THE ROLE OF YEASTS AND PSYCHROTOLERANT ORGANISMS TO ICY MOON HABITABILITY AND PLANETARY PROTECTION

Kurzfassung

Yeasts and other psychrotolerant microorganisms play a key role in astrobiology research. These species, capable of growing at subzero temperatures, are of particular relevance to investigations focusing on the icy moons of the solar system. Exploring how these microorganisms adapt to subzero temperatures and to space conditions might reveal whether Earth life can survive on the icy moons. Therefore, providing habitability insights as well as consideration for forward planetary protection. These considerations are especially important given the interest in these locations by missions such as NASA’s Europa Clipper and ESA’s JUICE (Jupiter Icy Moons Explorer). Despite these missions not being landers, we must ensure the up-to-date knowledge regarding survival and other metabolic mechanisms by Earth-originating (psychrotolerant) material in order to safeguard future surface missions from contaminating the local environment. To this end, our previous research showed how different eukaryotic and prokaryotic psychrophilic and psychrotolerant microorganisms tolerate extreme space conditions (freeze and thaw cycles, desiccation, X-ray and UV-C and polychromatic UV radiation) when grown in oligotrophic media. Our results also showed how the selected yeasts are more resilient than the selected bacteria. For this reason, to identify the most relevant mechanisms for survival, we selected the yeast Rhodotorula frigidalcoholis for further transcriptomic investigations. The analysis of the yeast’s transcriptome included the exposure of the microorganism to combined icy moon conditions (desiccation, X-ray and polychromatic UV radiation) after growth in minimal media supplemented only with glutamic acid as a carbon source. Our analysis showed that the yeast has a high differential expression of genes under all the experimentalconditions. Additionally, we have seen how the yeast expresses genes under desiccation, including upregulating genes responsible for halting cell cycle progression. Furthermore, the yeast sample allowed to repair at optimal temperature after exposure to icy moon conditions, showed how the microorganism upregulates a high number of catalytic activity and DNA repair genes, this includes the well-studied DNA photolyase. Our research underscores the importance of transcriptomic analyses for astrobiology research, especially ones focusing on psychrotolerant microorganisms. It also shows the relevance of eukaryotic microorganisms as microbial candidates for icy moon research.