engleski

Uncovering the microbial communities in geothermal springs of Daruvarske Toplice (Croatia)

Background: Microbial communities in natural geothermal springs represent an excellent example of microorganisms inhabiting extreme environments. Geothermal ecosystems present poorly investigated habitats in Croatia. The biodiversity in such environments depends on temperature and pH, but also different nutrient concentrations. Nitrogen and sulfur, in particular, are often crucial factors in determining microbial community structure. Objectives: The primary objective was to analyze the diversity of thermotolerant and thermophilic microorganisms in the geothermal springs of Daruvarske Toplice through different seasons, and to identify abiotic factors that shape the microbial community composition. Methods: Two hot springs (Antunovo vrelo and Ivanovo vrelo) and one well (Marijino vrelo) located in Daruvarske Toplice were selected for sample collection during three seasons. Physical parameters were measured in situ, as well as H2S concentrations. Other parameters were analyzed in the laboratory immediately after field sampling. After water filtering, DNA extraction, and PCR amplification, we analyzed the 16S rRNA gene diversity obtained using high throughput sequencing techniques. All statistical analyses were performed in the R environment. Results: Antunovo vrelo had the most stable community structure during all three sampling seasons and was dominated by microorganisms affiliated with the phyla Crenarchaeota, Proteobacteria, and Nitrospirota. In contrast, most bacterial ASVs in Ivanovo vrelo were affiliated to Bateroidota and Proteobacteria, while the bacterial community at Marijino vrelo was most diverse, with sequences of the phylum Proteobacteria dominating during all three seasons. On the genus level, the most abundant were ammonia-oxidizing archaea of the genera Candidatus Nitrosotenuis and Candidatus Nitrososphaera, as well as nitrite-oxidizing Nitrospira and sulfur-oxidizing Sulfuricurvum. Our results indicated that inorganic nitrogen and sulfur compound concentrations, along with correlating temperature and pH were the main drivers for microbial community composition.

hot springs ; microbial communities ; 16S rRNA ; extremophiles

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