Linking Microbial Community Structure to S, N and Fe Biogeochemical Cycling in the Hot Springs at the Tengchong Geothermal Fields, Southwest China

Sediment and water samples collected from one acidic and three alkaline high temperature hot springs at the Tengchong terrestrial geothermal field, Southwest China, were examined using mineralogical, geochemical, and molecular biological techniques. The mineralogical and geochemical analyses suggested that these hot springs contained relatively high concentrations of S, Fe and N chemical species. Specifically, the acidic water was rich in Fe²⁺, SO₄²⁻ and NH₄⁺, while the alkaline waters were high in NO₃⁻, H₂S and S₂O₃⁻. Analyses of 16S rRNA gene sequences showed their bacterial communities were dominated by phyla <i>Aquificae, Cyanobacteria, Deinococci-Thermus, Firmicutes, Proteobacteria</i>, and <i>Thermodesulfobacteria</i>, while the archaeal clone libraries were dominated by orders <i>Desulfurococcales, Sulfolobales</i>, and <i>Thermoproteales</i>. Potential S-, N- and Fe-metabolizing prokaryotes were present at a relatively high proportion, but with large differences in the diversity and metabolic functions of each sample. These findings provide implications for uncovering microbial functions in elemental biogeochemical cycles within the Tengchong geothermal environments: <i>i).</i> the distinct differences in abundance and diversity of microbial communities in geothermal sediments were related to different <i>in situ</i> physicochemical conditions; <i>ii).</i> the S-, N- and Fe-related prokaryotes would take advantage of the strong chemical disequilibria in the hot springs; and <i>iii).</i> in return, their metabolic activities could promote the transformation of the S, Fe and N chemical species, thereby forming the basis of biogeochemical cycles in the terrestrial geothermal environments.