Abstract EANA2024-21

Cryptoendolithic communities are microbial ecosystems dwelling inside porous rocks perpetuating at the edge of life sustainability in the ice-free areas of the Antarctic desert (Friedmann, 1982; Cary et al. 2010). These regions include the McMurdo Dry Valleys, often accounted as the closest terrestrial counterpart of the Martian environment (Cockell et al. 2016) and thought to be devoid of life until the discovery of these cryptic life-forms, which reshaped current concepts regarding the limits of life on our planet. These communities are very stable due to the nature of the rock matrix and display a physiological very slow growth rate, further slowed down in the permanent stressing conditions in their natural environment; therefore, their structure and functionality are the result of a long evolution and optimal adaptation to specific environmental conditions. Yet, despite their interest as a model for the early colonization of Earth, adaptation to extreme conditions and for speculating the possibility of life beyond Earth, little was known about the evolution, diversity, and genetic makeup of species that reside in these environments (Coleine et al. 2018; Archer et al. 2017). To address this knowledge gap, we generated the first catalogues of metagenomes from rocks collected in the Antarctic desert, spanning a broad range of environmental and spatial conditions over a distance of about 350 km along an altitudinal transect from 834 up to 3,100 m above sea level (a.s.l.) and different solar exposures (Albanese et al. 2021; Ettinger et al. 2023; Coleine et al. 2024). We significantly increased the repertoire of genomic data for several taxa, including fungi, algae, bacteria and viruses. We found largely undescribed, highly diverse and spatially structured viruses communities, comprising > 75,000 viral operational taxonomic units (vOTUS), which had predicted auxiliary metabolic genes (AMGs) with functions indicating that they may be potentially influencing adaptation and biogeochemistry of the other microbial components of the community (Ettinger et al. 2023). We further reconstructed 4,539 metagenome-assembled genomes, 49.3 % of which were novel candidate bacterial species and we found that they might represent evolutionary remnants of pristine clades that evolved across the Tonian glaciation (Albanese et al. 2021). We untangled the main adaptation strategies that allow the persistence of these microorganisms at the fringe of life and we found that a few alternative of them such as the trace gas oxidation and atmospheric chemosynthesis are prevalent supporting predicted metabolic activity (Coleine et al. 2024; Williams et al. 2024). These results laid the foundation for the for the realization of the multidisciplinary project CRYPTOMARS (Italian Space Agency, Principal Investigator: Laura Selbmann), where biological, chemical and physical approaches will be implemented on a selection on a wide selection Antarctic rocks, from colonized to fossilized samples, to provide the foundational principles needed to predict the bulk of features characterizing microbial assemblages potentially able to colonize early or present Mars environment.