Highly differentiated soil bacterial communities in Victoria Land macro-areas (Antarctica)

Antarctica is one of the most physically and chemically demanding environments on Earth. Only 0.34% (44,000 km2) of the continent is seasonally or permanently free of ice. Ice-free areas include the lower-latitude Antarctic Peninsula on the West side, high-altitude mountain peaks of the Ellsworth and Transantarctic Mountains and of the highest mountains in East Antarctica, coastal sites, isolated nunataks, and the McMurdo Dry Valleys.Victoria Land covers a latitudinal gradient of approximately 8 grades, and extends from the Ross Sea to the edge of the Polar Plateau. It is one of the 15 biologically distinct, ice-free, Antarctic Conservation Biogeographic Regions (ACBRs), encompassing the continent and close-lying islands. This region hosts a wide range of different niches, with minimal human perturbations, suitable for microbial colonization. Antarctic soils contain a high level of microbial diversity, however limited attention has so far been given to microorganisms living in Antarctic terrestrial ecosystems. With this study, we aimed to give new insights into Victoria Land soil ecosystems, providing an extensive characterization of bacteria associated to soils and BSCs along a wide latitudinal gradient, through the analysis of 60 samples from 14 localities. Microbiome sequencing was performed amplifying the V3-V4 hypervariable region of the 16S rRNA gene. The 14 localities were grouped in three macrohabitats, namely coastal sites, characterized by the presence of BSCs, inner sites in Dry Valleys with soils without evident colonizations and a third site close to the "Mario Zucchelli" Italian Base, named "Icarus Camp", where samples were collected from initial steps of a surface alteration of granite sheets slightly sloping towards the sea.