Tibetan near-neutral hot spring samples Targeted Locus (Loci)

Tibet Plateau in Southwest China hosts a number of hot springs and they represent a biodiversity hotspot for thermophiles, yet only a very limited number of molecular-based studies are currently available to study microbial diversity and community structure in these habitats. In this study we investigated microbial diversity and community composition in hot springs with a wide range of temperatures (22.1~75oC) by using 16S rRNA gene fragment pyrosequencing. Sequence analysis revealed that bacteria (95% of total sequences) in Tibetan hot springs were more abundant than archaea and far more diverse than previously reported. The dominant bacterial phyla systematically varied with temperature. Moderate temperatures (66~75oC) favored Aquificae, GAL35, and novel bacteria, whereas low temperatures (22.1~60oC) favored Deinococcus-Thermus, Cyanobacteria, and Chloroflexi. The relative abundances of these phyla varied with temperature, showing a positive correlation of Aquificae with temperature and a negative correlation of Deinococcus-Thermus, Cyanobacteria, and Chlorofelxi with temperature. Cyanobacteria and Chloroflexi were abundant in Tibetan hot springs and the relationship between these two phyla was either competitive at low temperatures (43~49oC) or cooperative at moderate temperatures (55~75oC). Most archaeal sequences were related to Crenarchaeota with only a few sequences related to Euryarchaeota and Thaumarchaeota. Despite the fact that the microbial composition was strongly shaped by temperature, microbial diversity (richness, evenness and Shannon diversity) was not significantly correlated with temperature. The results of this study expand our understanding of microbial ecology in Tibetan hot springs and provide a basis for a global comparison.