Characterization of prokaryotic communities from Italian super-heated fumaroles.

Among extremophiles, thermophile microorganisms from geothermal sites have been widely studied. Nevertheless, our knowledge is still relatively poor on microbial communities colonizing fumaroles, which are super-ephemeral habitats, characterized by an only intermittent presence of water. Here we characterized by metabarcoding both bacterial and archaeal communities from hot spring waters and biofilms, together with dry and wet fumaroles, of a geothermal basin in central Italy. Taxa composition of the analyzed samples mirrored that of previous studies, with Thermoproteota dominating among Archaea, while high percentages of thermophiles and spore-forming organisms were retrieved for Bacteria. Cyanobacteriota were the dominant group in biofilms. Community structure was different in the two domains, with highly selected communities of Archaea, less diversified than bacterial ones. Linear regression analyses highlighted significant correlations between diversity and environmental parameters in dry, but not in wet fumaroles. Although ASV numbers displayed different trends for the two different prokaryotic domains (positive correlation with pH for Bacteria, negative correlation for both pH and T for Archaea), such results indicate that even an extremely ephemeral presence of water can influence the importance of temperature and pH as drivers for microbial community structure.