Abundance and Diversity of Sulfur-Oxidizing Bacteria along a Salinity Gradient in Four Qinghai-Tibetan Lakes, China

Abstract Sulfur-oxidizing bacteria (SOB) play important roles in the sulfur cycle and are widespread in a number of environments, but their occurrence and relationship to geochemical conditions in (hyper)saline lakes are still poorly understood. In this study, the abundance and diversity of SOB populations were investigated in four Qinghai-Tibetan lakes (Erhai Lake, Gahai Lake 1, Gahai Lake 2 and Xiaochaidan Lake) by using quantitative polymerase chain reaction (qPCR) and soxB gene- (encoding sulfate thiohydrolase) based phylogenectic analyses. qPCR analyses showed that in the studied lakes, the total bacterial 16S rRNA and soxB gene abundances in the sediments were distinctly higher than in the overlying waters. The 16S rRNA gene abundance in the waters ranged 5.27 × 106–6.09 × 108 copies per mL and 7.39 × 1010–2.9 × 1011 copies per gram sediment. The soxB gene abundance in the waters ranged from 1.88 × 104 to 5.21 × 105 per mL and 4.73 × 106–2.65 × 107 copies per gram sediment. The soxB gene in the waters of the two hypersaline lakes (Gahai Lake 2 and Xiaochaidan Lake) was more abundant (2.97 × 105 and 5.21 × 105 copies per mL) than that in the two low-salinity lakes (1.88 × 104 and 3.36 × 104 copies per mL). Phylogenetic analysis showed that Alpha- and Betaproteobacteria were dominant SOB in the investigated lakes, and the composition of proteobacterial subgroups varied with salinity: in freshwater Erhai Lake and low-salinity Gahai Lake 1, the SOB populations were dominated by the Betaproteobacteria, whereas in hypersaline Lake Gahai 2 and Xiaochaidan Lake, the SOB populations were dominated by Alphaproteobacteria. Overall, salinity played a key role in controlling the diversity and distribution of SOB populations in the investigated Qinghai-Tibetan lakes. Keywords: Qinghai-Tibetan lakessulfur-oxidizing bacteriasulfur cycle soxB Acknowledgments This research was supported by the National Natural Science Foundation of China (Grant Nos. 41002123, 41030211 and 41121001), the National Basic Research Program of China (Grant No. 2011CB808800), State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (No. GBL11201), the Fundamental Research Funds for National University, China University of Geosciences (Wuhan), and the One-hundred Talent Project (A0961) of CAS grant to ZPL. We are grateful to Huanye Wang at the Institute of Earth Environment, Chinese Academy of Sciences and Jinxiang Wang at Tongji University for help with sample collection. We are grateful to two anonymous reviewers whose constructive comments significantly improved the quality of the manuscript.