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 NH4C, 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 Aquificae, Cyanobacteria, Deinococci-Thermus, Firmicutes, Proteobacteria, and Thermodesulfobacteria, while the archaeal clone libraries were dominated by orders Desulfurococcales, Sulfolobales, and Thermoproteales. 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). the distinct differences in abundance and diversity of microbial communities in geothermal sediments were related to different in situ physicochemical conditions; ii). the S-, N- and Fe-related prokaryotes would take advantage of the strong chemical disequilibria in the hot springs; and iii). 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.