Distribution of ether lipids and composition of the archaeal community in terrestrial geothermal springs: impact of environmental variables

Abstract

Archaea can respond to changes in the environment by altering the composition of their membrane lipids, for example, by modification of the abundance and composition of glycerol dialkyl glycerol tetraethers (GDGTs). Here, we investigated the abundance and proportions of polar GDGTs (P-GDGTs) and core GDGTs (C-GDGTs) sampled in different seasons from Tengchong hot springs (Yunnan, China), which encompassed a pH range of 2.5-10.1 and a temperature range of 43.7-93.6°C. The phylogenetic composition of the archaeal community (reanalysed from published work) divided the Archaea in spring sediment samples into three major groups that corresponded with spring pH: acidic, circumneutral and alkaline. Cluster analysis showed correlation between spring pH and the composition of P- and C-GDGTs and archaeal 16S rRNA genes, indicating an intimate link between resident Archaea and the distribution of P- and C-GDGTs in Tengchong hot springs. The distribution of GDGTs in Tengchong springs was also significantly affected by temperature; however, the relationship was weaker than with pH. Analysis of published datasets including samples from Tibet, Yellowstone and the US Great Basin hot springs revealed a similar relationship between pH and GDGT content. Specifically, low pH springs had higher concentrations of GDGTs with high numbers of cyclopentyl rings than neutral and alkaline springs, which is consistent with the predominance of high cyclopentyl ring-characterized Sulfolobales and Thermoplasmatales present in some of the low pH springs. Our study suggests that the resident Archaea in these hot springs are acclimated if not adapted to low pH by their genetic capacity to effect the packing density of their membranes by increasing cyclopentyl rings in GDGTs at the rank of community.

Localized high abundance of Marine Group II archaea in the subtropical Pearl River Estuary: implications for their niche adaptation

“…Clustering of samples by archaeal community composition was performed using the base program in R 2.12.1. The relative abundance of archaeal phylotypes based on 16S rRNA gene sequences was imported into R and the distance matrix was computed with the squared Euclidean distance using the two-way joining method (Xie et al, 2014a). A hierarchical clustering tree was generated by the Heatmap command in R (Maindonald, 2007).…”

Molecular adaptation of ammonia monooxygenase during independent pH specialization in Thaumarchaeota

“…, ; Xie et al . ), which is thought to reduce the influx of protons in acidic environments (López de Saro et al . ).…”

“…The number of GDGT cyclopentane rings correlates inversely with pH (e.g. Macalady et al 2004;Pearson et al 2008;Boyd et al 2011Boyd et al , 2013Xie et al 2015), which is thought to reduce the influx of protons in acidic environments (L opez de Saro et al 2015). Therefore, as a study premise, we postulate that modifications to lipid membrane conformation required under different pH conditions necessitates adaptations in membrane localized proteins, including ammonia monooxygenase, to maintain essential protein functions and protein-protein interactions, along with normal protein folding.…”

Temporal variation in community structure and lipid composition of Thaumarchaeota from subtropical soil: Insight into proposing a new soil pH proxy

“…Other environmental investigations have also demonstrated that the resident Archaea in terrestrial hot springs effect change in the packing density of their membranes in response to low pH, by increasing the cyclopentyl rings in GDGTs at the rank of community (Boyd et al, 2013;Xie et al, 2014a).…”

“…This approach has, however, been used to study archaeal and bacterial biogeochemical process in hot springs Xie et al, 2014a). The aim of this study, therefore, was to examine on one hand temporal variation in core ether lipids and archaeal communities and, on the other hand, how they respond to seasonal changes in environmental conditions at a subtropical soil site.…”