Distinct microbial composition and functions in an underground high-temperature hot spring at different depths

Abstract. The microbial diversity and functions of three high-temperature neutral hot springs water samples at different depths (0 m, 19 m and 58 m) were investigated based on 16S rRNA gene sequencing and a functional gene array (GeoChip 5.0). The results revealed that the bacterial communities were distinct at different depths in the hot springs. Additionally, in response to the depths, bacterial/archaeal community compositions exhibited shifts over the depth profiles. Aquificae, Alpha-proteobacteria, and Deinococcus-Thermus were the dominating phyla at 0 m, 19 m, and 58 m, respectively. Hydrogenobacter, Sphingobium, and Thermus were the most abundant genera at 0 m, 19 m, and 58 m, respectively. The phylum Thaumarchaeota was the most abundant member of the archaeal community in the samples at different hot spring depths. Functional results of the microbial communities indicated that microbial metabolic functions were mainly related to sulfur, nitrogen cycling, and hydrogen oxidation. In summary, our results demonstrated that distinct microbial communities and functions were found at different depths of hot springs in a very limited area. These findings will provide new insights into the deep-subsurface biosphere associated with terrestrial hot springs.