Comprehensive glycerol ether lipid fingerprints through a novel reversed phase liquid chromatography–mass spectrometry protocol

Abstract

Glycerol ether lipids have been developed as proxies to reconstruct past environmental changes or in their intact polar form to fingerprint the viable microbial community composition. However, due to the structural complexity, the full characterization of glycerol ether lipids requires separate protocols for the analysis of the polar head groups and the alkyl chain moieties in core ether lipids. As a consequence, the valuable relationship between core ether lipid composition and specific polar head groups is often lost; this limits our understanding of the diversity of ether lipids and their utilities as biogeochemical proxies. Here, we report a novel reverse-phase liquid chromatography-electrospray ionization-mass spectrometry (RP-ESI-MS) protocol that enables the simultaneous analysis of polar head groups (e.g., phosphocholine, phosphoglycerol, phosphoinositol, hexose, and dihexose) and alkyl moieties (e.g., alkyl moieties modified with different numbers of cycloalkyl moieties, hydroxyl and alkyl groups, and double bonds) in crude lipid extracts without further preparation. This protocol greatly enhances the detection of archaeal intact polar lipids (IPLs) and core lipids (CLs) with double-bond-and hydroxyl-group-bearing alkyl moieties. With these improvements, widely used ratios that describe relative distribution of the core lipid, such as the TEX 86 and ring index, can now be directly determined in specific intact polar lipids (IPL-specific TEX 86 and ring index). Since IPLs are the putative precursors of the environmentally persistent core lipids, their detailed examination by this protocol can potentially provide new insights into diagenetic and biological mechanisms inherent to these proxies. In a series of 12 samples from diverse settings, core and IPL-specific TEX 86 values follow the order: 2G-GDGTs > core GDGTs > 1G-GDGTs > 1G-GDGT-PI; and the ring indices follow: 1G-GDGTs ≈ core GDGTs > 2G-GDGTs > 1G-GDGT

The novel extremely acidophilic, cell-wall-deficient archaeon Cuniculiplasma divulgatum gen. nov., sp. nov. represents a new family, Cuniculiplasmataceae fam. nov., of the order Thermoplasmatales

“…in 5 min, followed by a gradient to 65 % B in 55 min. The column was then flushed with 90 % B for 10 min and re-equilibrated with 100 % A for 10 min (Zhu et al, 2013). Lipid identification was based on retention time as well as accurate molecular mass and isotope pattern match with known sum formulas in full scan mode and MS2 fragment spectra.…”

Cellular content of biomolecules in sub-seafloor microbial communities

“…coupled to an ABSCIEX QTRAP 4500 mass spectrometer (ABSCIEX, Darmstadt, Germany) by a TurboIonSpray ion source set to electrospray ionization (ESI) mode. The samples were chromatographically separated on an ACE3 C 18 column (150 × 2.1 mm; particle size 3 µm) equipped with a guard column using a method modified from Zhu et al (2013). Column temperature was set to 45 °C and eluent A consisted of MeOH/HCO 2 H/14.8 M NH 3 and eluent B was prepared from propan-2-ol/HCO 2 H/14.8 M NH 3 .…”

The archaeal lipidome in estuarine sediment dominated by members of the Miscellaneous Crenarchaeotal Group

“…To this end, Buckles and colleagues (2013) suggested that relative enrichments of an archaeal tetraether lipid, the taxonomically widely distributed glycerol dibiphytanyl glycerol tetraether without cyclopentane rings [i.e. Fortunately, recent advances in the analysis of intact polar lipids (IPLs; Sturt et al, 2004;Wörmer et al, 2013;Zhu et al, 2013) and core lipids (CLs; Knappy et al, 2009;Liu et al, 2012a,b;Becker et al, 2013;Zhu et al, 2014a,b) have already expanded the catalogue of microbial biomarkers and enhanced the ability to find biomarkers associated with the presence of MCG, which could lead to the identification of specific lipid biomarkers. However, the utility of GDGT(0) as universal biomarker for MCG is severely limited due to the widespread occurrence of this lipid in many archaeal phyla (e.g.…”