Bacterial And Archaeal Taxonomic Diversity Of Mud Volcanoes (Beciu, Romania) Via Metagenomic Approach

Terrestrial mud volcanoes usually develop in overpressured, hydrocarbon-bearing sedimentary basins where argillaceous, viscous fluids and gases find passages to the surface. In this study mud samples collected at the Beciu mud volcano area (Romania) were examined using 16S rRNA gene amplicon sequencing technique. Bacterial communities were dominated by Proteobacteria, Patescibaceria, Bacteriodota, and Campilobacterota while Archaea by Halobacterota and Nanoarchaeota. All the most abundant taxa can be connected to the characteristic methane production of the onshore mud volcanism and/or the presence of a deep subsurface salt layer. The discharged methane might be utilized by the detected ubiquitous anaerobic methane oxidizers (ANME-1, ANME-2a-2b, ANME-3) coupling the reaction with the sulfate or sulfur reduction by representatives of genera Sulfurovum, Sulfurimonas, Desulfobacterales, Desulfuromonadales, Halanaeroarchaeum, and Halodesulfurarchaeum. In addition to methanotrophs, methylotrophic and acetoclastic methanogens were also detected. Most of the identified OTUs were associated with halophilic taxa. The results suggest that prokaryotes inhabiting the mud volcanoes can be participated in the closely interconnected methane and sulfur cycles.