http://www.sciencedirect.com/science/article/pii/S1674987111001332

Isoprenoidal glycerol dialkyl glycerol tetraethers (iGDGTs) from the Gulu hot springs(23e83.6 C, pH>7) andYangbajing hot springs (80e128 C, pH>7) were analyzed in order to investigatethe distribution of archaeal lipids among different hot springs in Tibet.Asoil sample fromGulu was incubatedat different temperatures and analyzed for changes in iGDGTs to help evaluate whether surrounding soil maycontribute to the iGDGTs in hot springs. The sources of bacterialGDGTs (bGDGTs) in these hot springs werealso investigated. The results revealed different profiles of iGDGTs betweenGulu andYangbajing hot springs.Core iGDGTs and polar iGDGTs also presented different patterns in each hot spring. The PCA analysisshowed that the structure of polar iGDGTs can be explained by three factors and suggested multiple sourcesof these compounds. Bivariate correlation analysis showed significant positive correlations between polar andcore bGDGTs, suggesting the in situ production of bGDGTs in the hot springs. Furthermore, in the soil incubationexperiment, temperature had the most significant influence on concentration of bGDGTs rather thaniGDGTs, and polar bGDGTs had greater variability than core bGDGTs with changing temperature. Ourresults indicated that soil input had little influence on the composition of GDGTs in Tibetan hot springs.On the other hand, ring index and TEX86 values were both positively correlated with incubation temperature,suggesting that the structure of archaeal lipids changed in response to varying temperature during incubation.