Impacts of temperature and pH on the distribution of archaeal lipids in Yunnan hot springs, China

Abstract

In culture experiments and many low temperature environments, the distribution of isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) commonly shows a strong correlation with temperature; however, this is often not the case in hot springs. We studied 26 hot springs in Yunnan, China, in order to determine whether temperature or other factors control the distribution of GDGTs in these environments. The hot springs ranged in temperature from 39.0 to 94.0°C, and in pH from 2.35 to 9.11. Water chemistry including nitrogen-, sulfur-, and iron species was also determined. Lipids from the samples were analyzed using liquid chromatography-mass spectrometry (LC-MS). Distributions of GDGTs in these hot springs were examined using cluster analysis, which resulted in two major groups. Group 1 was characterized by the lack of dominance of any individual GDGTs, while Group 2 was defined by the dominance of GDGT-0 or thaumarchaeol. Temperature was the main control on GDGT distribution in Group 1, whereas pH played an important role in the distribution of GDGTs in Group 2. However, no correlations were found between the distribution of GDGTs and any of the nitrogen-, sulfur-, or iron species. Results of this study indicate the dominance of temperature or pH control on archaeal lipid distribution, which can be better evaluated in the context of lipid classification.

Keywords: Archaea; GDGTs; Yunnan; hot springs; organic proxies; pH; temperature.

FIGURE 1

A geographic map of the locations of hot springs in Yunnan, China.

FIGURE 2

HPLC–APCI–MS base peak chromatograms showing representative distributions of archaeal core lipids with temperature and pH values (A) and chemical structures of GDGTs from Yunnan hot springs (B). TC-5, Zhenzhuquan; LL-4, Banglazhangshangxiao #1; EY-4, Niujieyongpingshougongjing; LL-2, Dahebianzaotang; TC-6, Gumingquan; TC-4, Yanjingquan. GDGTs from acidic hot springs with medium high temperature were dominated by GDGTs with more cyclopentyl rings, such as TC-5, LL-4, and EY-4, while those from neutral alkaline hot springs were dominated by GDGTs with fewer cyclopentyl rings, such as LL-2, TC-6, and TC-4. Thaum.isomer, Thaumarchaeol regioisomer. The relative abundance of thaumarchaeol to GDGT-4 for each sample was marked in each chromatograph.

FIGURE 3

Cluster analysis of archaeal lipids in hot spring sediments by R clustering method. Sample names are shown on the right of the figure. GDGTs are color coded and shown at the bottom of the figure. TC-1, Dagunguo; TC-2, Diretiyanqu; TC-3, Yanjingquan; TC-4, Yanjingquan; TC-5, Zhenzhuquan; TC-6, Gumingquan; TC-7, Dawumingquan; TC-8, Wumingxiaoxishangyou; TC-9, Wumingxiaoxizhongyou; TC-10, Hamazui; LL-1, Dahebianzhongyou; LL-2, Dahebianzaotang; LL-3, Banglazhangshangxiao #1; LL-4, Banglazhangshangxiao #1; LL-5, Banglazhangshangxiao #3; LL-6, Banglazhangshangxiao #5; LL-7, Banglazhangshangxiao #6; LL-8, Banglazhangshangxiao #8; LL-9, Xiaoxiaqiangxia, EY-1, Xiashankouchitang, EY-2, Xiashankoudaotian, EY-3, Niujieyongpingzaotang, EY-4, Niujieyongpingshougongjing, EY-5, Shibeicunlaizitang #1; EY-6, Shibeicunlaizitang #2; AN-1, Tianxiadiyitang.

FIGURE 4

Correlations between organic proxies and environmental parameters using total samples. (A) Thaum/(Thaum + GDGT-0) and temperature; (B) MI and temperature; (C) RI and temperature. Thaum, Thaumarchaeol.

FIGURE 5

Correlations between organic proxies and environmental parameters in two clustering groups according to Figure 3. (A) Thaum/ (Thaum + GDGT-0) and temperature in Group 1; (B) MI and temperature in Group 1; (C) Thaum/(Thaum + GDGT-0) and pH in Group 2. Thaum, Thaumarchaeol.

FIGURE A1

Clustering results from Yunnan hot springs by principal component analysis. Solid circles with brown, yellow, blue, and red color represent samples from Group 1.1, Group 1.2, Group 2.1, and Group 2.2 in Figure 3, respectively. Thaum, Thaumarchaeol, Thaum. i, Thaumarchaeol isomer.

FIGURE A2

Cluster analysis of archaeal lipids from Yunnan hot spring sediments in this study and surrounding soils (Xie et al., unpublished data). Samples named with “S” are from soils surrounding hot springs. TC-1, Dagunguo; TC-2, Diretiyanqu; TC-3, Yanjingquan; TC-4, Yanjingquan; TC-5, Zhenzhuquan; TC-6, Gumingquan; TC-7, Dawumingquan; TC-8, Wumingxiaoxishangyou; TC-9, Wumingxiaoxizhongyou; TC-10, Hamazui; LL-1, Dahebianzhongyou, LL-2, Dahebianzaotang, LL-3, Banglazhangshangxiao #1; LL-4, Banglazhangshangxiao #1; LL-5, Banglazhangshangxiao #3; LL-6, Banglazhangshangxiao #5; LL-7, Banglazhangshangxiao #6; LL-8, Banglazhangshangxiao #8; LL-9, Xiaoxiaqiangxia; EY-1, Xiashankouchitang; EY-2, Xiashankoudaotian; EY-3, Niujieyongpingzaotang; EY-4, Niujieyongpingshougongjing; EY-5, Shibeicunlaizitang #1; EY-6, Shibeicunlaizitang #2; AN-1, Tianxiadiyitang; Srbz 1, Shuirebaozao #1; Srbz 2, Shuirebaozao #2; Jmq, Jiemeiquan, Wmql, Wumingquan left; Srbz, Shuirebaozao; Zzqr, Zhenzhuquan right; DrtyC, Diretiyan # C; DrtyD, Diretiyan #D; DrtyG, Diretiyan #G; DrtyF, Diretiyan #F; Jmqr, Jiemeiquan right; Gmqd, Gumingquan down; Jz, Jieming; Gxs, Gongxiaoshe.