Abstract_EANA2024-20

Abstract EANA2024-20

Microbial Diversity in Antarctic Granite: Insights into Endolithic and Epilithic Communities and Their Implications for Mars Analog Studies

Gerardo A. Stoppiello 1 , Roberto De Carolis 2 , Lucia Muggia 1 , Claudia Coleine 2 , Laura Selbmann 2,3

1 Department of Life Sciences, University of Trieste, via L. Giorgieri 10, 34127 Trieste, Italy 2 University of Tuscia, Largo dell’Università, Department of Ecological and Biological Sciences, 01100 Viterbo, Italy 3 Italian Antarctic National Museum (MNA), Mycological Section, Genoa, Italy

In the driest and coldest ice-free areas of continental Antarctica, addressed as the closest terrestrial
analogue of Martian environment (e.g., in the McMurdo Dry Valleys or mountain peaks cropping
out from the Polar Plateau), the environmental conditions reach the limits for supporting life. There,
self-sustaining endolithic communities (i.e., microbial communities living within rocks) often
represent the most significant, if not the sole, standing biomass. These guilds are commonly
considered as gold models to speculate both the chance of interplanetary transfer of propagules
through meteorites, as postulated in the Lithopanspermia theory, as well as the possibility for life
beyond Earth. Previous studies have considerably extended the general knowledge about their
biodiversity, evolution of new and peculiar taxa, and their extraordinary functionality and resistance
to multiple stresses. All these data contributed to understand the persistence of life at the edge on
Earth and facilitate new strategies in the quest for extant or extinct life on other rocky planets such
as Mars. However, most studies have been focused on communities inhabiting sandstones, while
data regarding biodiversity and community composition of granite samples are still negligible. To
address this knowledge gap, we used amplicon sequencing to characterize bacterial and fungal
assemblages in granite samples collected in Antarctica during the XXXVII Italian Expedition. We
further compare those samples with epilithic lichen communities collected in the same localities,
representing the first comparative analysis between these two ecologies and providing valuable
insights into their microbial diversity and composition. Our results revealed distinct differences
between endolithic and epilithic communities in terms of diversity and composition. In particular,
endolithic communities exhibited higher microbial diversity, likely influenced by a combination of
environmental factors and the complex interplay between lichens and other microorganisms.
Moreover, the endolithic niche was found to be highly selective for radio-resistant strains (e.g. a
few cyanobacterial species), highlighting the remarkable ability of endolithic substrate to harbor
extreme-adapted microorganisms. Overall, our findings shed light on the ecological dynamics of
microbial communities in extreme environments giving insights on the adaptive and evolutionary
processes of microbes towards the far extremes and Mars-like conditions.