Microbial Composition and Diversity Patterns in Deep Hyperthermal Aquifers from the Western Plain of Romania

Abstract

A limited number of studies have investigated the biodiversity in deep continental hyperthermal aquifers and its influencing factors. Here, we present the first description of microbial communities inhabiting the Pannonian and Triassic hyperthermal aquifers from the Western Plain of Romania, the first one being considered a deposit of "fossilized waters," while the latter is embedded in the hydrological cycle due to natural refilling. The 11 investigated drillings have an open interval between 952 and 3432 m below the surface, with collected water temperatures ranging between 47 and 104 °C, these being the first microbial communities characterized in deep continental water deposits with outflow temperatures exceeding 80 °C. The abundances of bacterial 16S rRNA genes varied from approximately 10-10 mL in the Pannonian to about 10-10 mL in the Triassic aquifer. A 16S rRNA gene metabarcoding analysis revealed distinct microbial communities in the two water deposits, especially in the rare taxa composition. The Pannonian aquifer was dominated by the bacterial genera Hydrogenophilus and Thermodesulfobacterium, together with archaeal methanogens from the Methanosaeta and Methanothermobacter groups. Firmicutes was prevalent in the Triassic deposit with a large number of OTUs affiliated to Thermoanaerobacteriaceae, Thermacetogenium, and Desulfotomaculum. Species richness, evenness, and phylogenetic diversity increased alongside with the abundance of mesophiles, their presence in the Triassic aquifer being most probably caused by the refilling with large quantities of meteoric water in the Carpathian Mountains. Altogether, our results show that the particular physico-cheminal characteristics of each aquifer, together with the water refilling possibilities, seem to determine the microbial community structure.

Identification, Characterization Enzymatic Antagonist Activity and Antimicrobial Resistance Profile of Bacteria Isolated From Brazilian Thermal Aquifer / Identificação, Caracterização Enzimática, Atividade Antagonista E Perfil De Resistência a Antimicrobianos De Bactérias Termotolerantes Isoladas Em Aquífero Termal Brasileiro

“…These findings are consistent with studies conducted in several hot springs and suggest that the presence of Bacillus in the sampled sites may be due to the ability of the genus to withstand adverse environmental conditions (Connor et al, 2010;Mohammad et al, 2017;Sahay et al, 2017;Yadav et al, 2018). Furthermore, the physical and chemical characteristics of the aquifer, the possibilities of water replenishment and sampling site seem to determine the microbial community present (Chiriac et al, 2017;Chiriac et al, 2018).…”

A deep continental aquifer downhole sampler for microbiological studies

“…These main OTUs are affiliated with Rhizobiaceae (Cluster_1), Burkholderiaceae (Cluster_2), Desulfurivibrionaceae (Cluster_5), Sphingomonadaceae (Cluster_6), Pseudomonadaceae (Cluster_7 and Cluster_13), Moraxellaceae (Cluster_8), and an unknown family (Cluster_9). These families have already been found in other deep continental anoxic environments and have been supposed to be involved in sulfur and nitrogen cycles (Mu et al, 2014;Chiriac et al, 2018;Nuppunen-Puputti et al, 2018;Soares et al, 2019;Bell et al, 2020). Because some of these families include bacteria described to be aerobic or nitrate-reducing, being certain of the quality of the sampling is essential.…”

Microbial Community Composition in Thermal Waters from the Lindian Geothermal Field (Songliao Basin, North-Eastern China)

“…A total of 677,437 original sequences were obtained by high-throughput sequencing of five samples in this study, and 21,377 OTUs were generated, among which 8298 OTUs were generated by the archaeal community (see Table S1), and 13,079 OTUs by the bacterial community (see Table S2), accounting for 32% and 68% of the whole microbial community, respectively. Generally, OTUs of geothermal waters are low, e.g., the OTUs of the thermal waters are 284-564, 49-2997, 224 and 2398 from the Xiongan New Area [45], TVZ [10], the Western Plain of Romania [46] and Sri Lanka [47], respectively. Thus, the total number of microbial taxa in thermal waters from the Lindian geothermal field is remarkably abundant, indicating abundant substrates, i.e., the high organic matter contents in the reservoir (Table 1).…”