Thermoplasmatales and Methanogens: Potential Association with the Crenarchaeol Production in Chinese Soils.

Fuyan Li,Weiguo Liu,Fengfeng Zheng,Chuanlun L Zhang,Yongli Wang

doi:10.3389/fmicb.2017.01200

Abstract

Crenarchaeol is a unique isoprenoid glycerol dibiphytanyl glycerol tetraether (iGDGT) lipid, which is only identified in cultures of ammonia-oxidizing Thaumarchaeota. However, the taxonomic origins of crenarchaeol have been debated recently. The archaeal populations, other than Thaumarchaeota, may have associations with the production of crenarchaeol in ecosystems characterized by non-thaumarchaeotal microorganisms. To this end, we investigated 47 surface soils from upland and wetland soils and rice fields and another three surface sediments from river banks. The goal was to examine the archaeal community compositions in comparison with patterns of iGDGTs in four fractional forms (intact polar-, core-, monoglycosidic- and diglycosidic-lipid fractions) along gradients of environments. The DistLM analysis identified that Group I.1b Thaumarchaeota were mainly responsible for changes in crenarchaeol in the overall soil samples; however, Thermoplasmatales may also contribute to it. This is further supported by the comparison of crenarchaeol between samples characterized by methanogens, Thermoplasmatales or Group I.1b Thaumarchaeota, which suggests that the former two may contribute to the crenarchaeol pool. Last, when samples containing enhanced abundance of Thermoplasmatales and methanogens were considered, crenarchaeol was observed to correlate positively with Thermoplasmatales and archaeol, respectively. Collectively, our data suggest that the crenarchaeol production is mainly derived from Thaumarchaeota and partly associated with uncultured representatives of Thermoplasmatales and archaeol-producing methanogens in soil environments that may be in favor of their growth. Our finding supports the notion that Thaumarchaeota may not be the sole source of crenarchaeol in the natural environment, which may have implication for the evolution of lipid synthesis among different types of archaea.

Highlights

Since the domain Archaea was proposed in 1977 (Woese and Fox, 1977), their biology, diversity and ecology have been widely studied
Our study indicates that uncultured representatives of Thermoplasmatales and archaeol-producing methanogens may be associated with production of crenarchaeol in soils in China dominated by these archaea
The 1G- and 2G-isoprenoid glycerol dibiphytanyl glycerol tetraether (iGDGT) fractions were identified in electrospray ionization (ESI) mode, which could only give relative abundance in peak areas

Summary

Introduction

Since the domain Archaea was proposed in 1977 (Woese and Fox, 1977), their biology, diversity and ecology have been widely studied. The intact polar lipids (IP-iGDGTs) containing sugar, phosphate or both head groups attached to the core lipids of iGDGTs (C-iGDGTs) have been found to degrade rapidly with cleavage of polar head groups after cell death (White et al, 1979; Harvey et al, 1986). They are commonly used as indicators for living microbes (Lipp et al, 2008; Lincoln et al, 2014), despite the possibility that glycolipids can be preserved over a geological timescale (Lengger et al, 2013, 2014). The C-iGDGTs, on the other hand, can be preserved in sediments over millions of years and have been widely used in paleoenvironment studies (Kuypers et al, 2001)

Methods

Results

Conclusion