The Distribution Of Archaeal Lipids In Tibetan Hot Springs

Tibetan Plateau is one of the highest places in the world with complex topography and little interference by humanity activities, which causes the place to be considered as one of the best ideals for the natural lab. The hydrothermal resources are rich with widely distributed hot springs. The complicated hot springs harbor various structure of microbial community with the high diversity of archaeal GDGT distributions. The diversity in distributions of environmental factor and microbial community is higher in the simple lake or marine systems than in the hot springs, resulting in the low diversity of archaeal GDGTs, which renders the lake or marine systems not to be as the ideal for the research of the relationship between archaeal GDGTs and environmental factors. So we choose Tibetan hot springs as the vector to analyze the characters in distributions of archaeal GDGTs and environmental factors and the correlations between the above two. The archaeal GDGTs and their correlations with temperature and pH were detected in the previous studies with the ignorance of other environmental factors. Based on the reason, we will systematically observe the multiple environment factors in the Tibetan hot springs.In this study, we collected 37 sediment samples from five hot springs and 5 soil samples near them. These hot springs had temperatures of 21.9℃ to 80℃ and pH values of 7 to 9.1. The occurrences and distribution of archaeal Polar-(P) and core-(C) iGDGTs were determined by high-performance liquid chromatography-mass spectrometry.Then we have the following conclusions. (i) by comparison of respective absolute concentrations and relative distributions expressed as TEX86 and ring index (R1) in P-GDGTs and C-GDGTs, we found that P and C-GDGTs were mainly in situ produced in hot springs. (ii) Cluster analysis showed the similarity in distributions of P and C-GDGTs in hot springs. Archaeal GDGTs can be separated into different groups based on the cluster analysis, which implicated different sources under different environmental conditions. (iii) Redundancy analysis and Pearson correlation analysis identified significant correlations among individual GDGTs and environmental factors including temperature, pH, nitrite, nitrate, sulfide, sulfate and phosphate. In particular, the responses of RI and TEX86 to sulfide and sulfate were much stronger than to temperature and pH in the P-GDGT fraction. On the other hand, C-GDGGTs had better responses to environmental factors than the P-GDGTs, suggesting that the core lipids may be more reliable for correlation analysis with environmental variables.