Microbial communities and novel taxa in « Continental Smokers » of northern Greece

Abstract

Analogously to the ocean-bottom black/white smokers, “continental smokers” have recently been defined as sites of mantle degassing through continental crust. The goal of this research, carried out within the Deep Carbon Observatory Community, is to investigate the role of deeplysourced fluids in niche ecosystem differentiation in European continental smokers. A 16S rRNA gene survey of microbial communities was carried out on 11 geothermal manifestations of northern Greece, all showing a distinct contribution of mantle fluids (R/Ra up to 1.2) that allow to classify them as continental smokers. The selected sites cover a wide range of temperatures (15-77 °C), pH (6.11-8.46), Eh (-289 – 40 mV), salinities (TDS 0.4-38 g/L) and show significant differences in energy sources for microbial life, like H2 (up to 0.8 μmol/L), CH4 (up to 400 μmol/L), NH4 (up to 112 μmol/L), sulphide (up to 103 μmol/L), Fe (up to 130 mmol/L). Illumina sequencing revealed negligible presence of Archaea and dominance of Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria. Different bacterial taxa dominate depending on physico-chemical features: Deinococcus-Thermus dominates the hottest sites while chemoautotrophic genera (Sulfurovum and Sulfurimonas) are abundant in the most reducing H2S-rich waters. Signatures of deep-sea vent microbial ecosystems were detected in most assemblages, together with novel taxa.