Characterization of prokaryotic communities from Italian super-heated fumaroles

Among extremophiles, thermophile microorganisms from geothermal sites have been widely studied, mostly from hot springs in extra-European locations. On the contrary, 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 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 Crenarchaeota dominating among Archaea, while high percentages of thermophiles and spore-forming organisms were retrieved for Bacteria. Cyanobacteria 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 a correlation in dry, but not in wet, fumaroles between pH and ASV number for Bacteria, and between both pH and temperature and ASV number for Archaea. Such result indicates that even an extremely ephemeral presence of water can influence the importance of temperature and pH as drivers for microbial community structure.