Mass spectrometric studies of ether lipids in Archaea and sediments

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been implemented as a means to separate and detect tetraether lipid cores derived from the complex lipids of Archaea. Distinct dissociation pathways during tandem mass spectrometry were noted for the lipid cores, providing information regarding their structure on-line. Analysis of cellular material from species of Methanothermobacter and Sulfolobus revealed tetraether lipid cores which contain up to four cyclopentyl rings per etherified alkyl chain, including structures identified previously in each genera. Identical structures were similarly identified in novel isolates from New Zealand hot springs. Product ions in the MS/MS spectra of the lipid cores include those formed from individual losses of both ring-containing C40 alkyl chains, allowing the reported structures to be verified with respect to the distribution of the rings within the two chains. A number of additional, hitherto unreported isomers and higher homologues of the ring-containing structures were resolved, both chromatographically and/or by characteristic product ions in MS/MS. Structures in which the two chains appear to be conjoined by a covalent link were also identified in Ignisphaera aggregans, the first such identifications in a Euryarchaeote. The array of structures revealed highlights both the complexity of the archaeal lipidome, which is more extensive than has been attributed previously, and the potential of LC-MS/MS as a powerful tool for probing tetraether lipid core structure. Ether lipid cores extracted from ancient aquatic sediments and contemporary soil were used to investigate the scope of LC-MS/MS for profiling of extremely complex distributions sourced from ecological communities as opposed to single organisms. Over 100 ether lipid components in total were identified during the studies, the vast majority of which represent novel structures. These include isoprenoid lipid cores of known archaeal origin and structures which may represent their transformation products; triolic structures in which one of the two capping glycerol moieties has been lost and chain or glycerol methylated higher homologues. A wealth of non-isoprenoid lipid cores were similarly identified, with inferred structures suggestive of a eubacterial or mixed eubacterial/archaeal origin. The components, once constrained to more specific origins, may be of chemotaxonomic value for use in modern environmental profiling or in palaeoecological reconstructions made using fossilised lipid cores

From ether to acid: a plausible degradation pathway of glycerol dialkyl glycerol tetraethers

Glycerol dialkyl glycerol tetraethers (GDGTs) are ubiquitous microbial lipids with extensive demonstrated and potential roles as paleoenvironmental proxies. Despite the great attention they receive, comparatively little is known regarding their diagenetic fate. Putative degradation products of GDGTs, identified as hydroxyl and carboxyl derivatives, were detected in lipid extracts of marine sediment, seep carbonate, hot spring sediment and cells of the marine thaumarchaeon Nitrosopumilus maritimus. The distribution of GDGT degradation products in environmental samples suggests that both biotic and abiotic processes act as sinks for GDGTs. More than a hundred newly recognized degradation products afford a view of the stepwise degradation of GDGT via (1) ether bond hydrolysis yielding hydroxyl isoprenoids, namely, GDGTol (glycerol dialkyl glycerol triether alcohol), GMGD (glycerol monobiphytanyl glycerol diether), GDD (glycerol dibiphytanol diether), GMM (glycerol monobiphytanol monoether) and bpdiol (biphytanic diol); (2) oxidation of isoprenoidal alcohols into corresponding carboxyl derivatives and (3) chain shortening to yield C39and smaller isoprenoids. This plausible GDGT degradation pathway from glycerol ethers to isoprenoidal fatty acids provides the link to commonly detected head-to-head linked long chain isoprenoidal hydrocarbons in petroleum and sediment samples. The problematic C80to C82tetraacids that cause naphthenate deposits in some oil production facilities can be generated from H-shaped glycerol monoalkyl glycerol tetraethers (GMGTs) following the same process, as indicated by the distribution of related derivatives in hydrothermally influenced sediments.Seventh Framework Programme (European Commission) (ERC Grant 247153

An interlaboratory study of TEX86 and BIT analysis of sediments, extracts and standard mixtures.

Two commonly used proxies based on the distribution of glycerol dialkyl glycerol tetraethers (GDGTs) are the TEX86 (TetraEther indeX of 86 carbon atoms) paleothermometer for sea surface temperature reconstructions and the BIT (Branched Isoprenoid Tetraether) index for reconstructing soil organic matter input to the ocean. An initial round-robin study of two sediment extracts, in which 15 laboratories participated, showed relatively consistent TEX86 values (reproducibility ±3-4°C when translated to temperature) but a large spread in BIT measurements (reproducibility ±0.41 on a scale of 0-1). Here we report results of a second round-robin study with 35 laboratories in which three sediments, one sediment extract, and two mixtures of pure, isolated GDGTs were analyzed. The results for TEX86 and BIT index showed improvement compared to the previous round-robin study. The reproducibility, indicating interlaboratory variation, of TEX86 values ranged from 1.3 to 3.0°C when translated to temperature. These results are similar to those of other temperature proxies used in paleoceanography. Comparison of the results obtained from one of the three sediments showed that TEX86 and BIT indices are not significantly affected by interlaboratory differences in sediment extraction techniques. BIT values of the sediments and extracts were at the extremes of the index with values close to 0 or 1, and showed good reproducibility (ranging from 0.013 to 0.042). However, the measured BIT values for the two GDGT mixtures, with known molar ratios of crenarchaeol and branched GDGTs, had intermediate BIT values and showed poor reproducibility and a large overestimation of the "true" (i.e., molar-based) BIT index. The latter is likely due to, among other factors, the higher mass spectrometric response of branched GDGTs compared to crenarchaeol, which also varies among mass spectrometers. Correction for this different mass spectrometric response showed a considerable improvement in the reproducibility of BIT index measurements among laboratories, as well as a substantially improved estimation of molar-based BIT values. This suggests that standard mixtures should be used in order to obtain consistent, and molar-based, BIT values

Design concepts for the Cherenkov Telescope Array CTA: an advanced facility for ground-based high-energy gamma-ray astronomy

Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA

Glycerol monoalkanediol diethers: A novel series of archaeal lipids detected in hydrothermal environments

Rationale: Recent advances in analytical techniques used to study archaeal membrane lipids have led to the identification of several novel di- and tetraether lipid structures. Here, we report the presence of a previously unknown series of archaeal diethers that have been detected exclusively in hydrothermally affected environments. Methods: Polar lipid extracts were analyzed using high-performance liquid chromatography coupled to positive ion atmospheric pressure chemical ionization mass spectrometry (HPLC/APCI-MS). Identification of the novel archaeal diethers was achieved using a triple quadrupole mass spectrometer operated in MS/MS mode and by comparison of characteristic retention time patterns. Results: Modern and fossil sediments deposited under hydrothermal conditions contained variable abundances of archaeal lipids including archaeol, glycerol trialkyl glycerol tetraether (GTGT-0), isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs), glycerol monoalkyl glycerol tetraethers (GMGTs) and glycerol dialkanol diethers (GDDs). In addition to these well-established archaeal lipids, we detected a novel series of archaeal diethers (i.e., glycerol monoalkanediol diethers (GMDs)) that are structurally related to GMGTs but which lack one terminal glycerol moiety and contain 0–2 cyclopentyl ring systems. Conclusions: The unique presence of GMDs in hydrothermally affected environments suggests that these compounds may constitute an exclusive and yet unknown component of the cell wall membrane of (hyper)thermophilic Archaea. The presented mass spectral characteristics will facilitate detection of these components in pure cultures of Archaea and natural environments

High-reflectance, high-durability coatings for IACT mirrors

Increased reflectance and longterm durability are major goals in the development of mirrors for CTA, the future observatory for very-high energy gamma-ray astronomy. Multilayer protective coatings on top of an aluminium coating and especially purely dielectric coatings show an increase in reflectance by 5 to 10% and a significantly better resistance to environmental impact simulations in the laboratory than aluminium coatings with a single SiO2 protective layer as are used in present day experiments

The major lipid cores of the archaeon Ignisphaera aggregans: implications for the phylogeny and biosynthesis of glycerol monoalkyl glycerol tetraether isoprenoid lipids

The lipid cores from Ignisphaera aggregans, a hyperthermophilic Crenarchaeon recently isolated from New Zealand hot springs, have been profiled by liquid chromatography– tandem mass spectrometry. The distribution revealed includes relatively high proportions of monoalkyl (also known as H-shaped) tetraether cores which have previously been implicated as kingdom-specific biomarkers for the Euryarchaeota. Such high expression ofmonoalkyl tetraether lipids is unusual in the archaeal domain and may indicate that formation of these components is an adaptive mechanism that allows I. aggregans to regulate membrane behaviour at high temperatures. The observed dialkyl tetraether and monoalkyl tetraether lipid distributions are similar but not fully concordant, showing differences in the average number of incorporated rings. The similarity supports a biosynthetic route to the ring-containing dialkyl and monoalkyl tetraether lipids via a dialkyl tetraether core containing zero rings, or a closely related structural relative, as an intermediate. Currently, however, the precise nature of the biosynthetic route to these lipids cannot be deduced

Distribution of glycerol ether lipids in halophilic, methanogenic and hyperthermophilic archaea

Four representatives of methanogenic Euryarchaeota (Methanosarcina mazei strain Gö1, Methanosphaera stadtmanae, Methanobrevibacter smithii and Methanosaeta thermophila), the hyperthermophilic euryarchaeon Thermococcus kodakarensis and the halophilic euryarchaeon Haloferax volcanii were studied for their glycerol ether lipid composition. The predominant core membrane lipid in all of them was archaeol, which was accompanied by variable quantities of sn-2-hydroxyarchaeol in the methanogens M. mazei (Methanosarcinales) and M. stadtmanae (Methanobacteriales). All methanogenic and hyperthermophilic Euryarchaeota also contained comparatively high abundances of the glycerol dialkyl glycerol tetraether without a cyclopentane moiety (GDGT-0). The methanoarchaeon M. stadtmanae, in addition to GDGT-0, contained GDGT core lipid structures with 1-4 cyclopentane moieties (GDGTs 1-4). We also found minor amounts of a glycerol trialkyl glycerol tetraether (GTGT) and a glycerol dialkanol diether (GDD), both of which did not contain cyclopentane moieties, as well as methylated and dimethylated GDGT-0 in all the archaea with the exception of H. volcanii. Like its GDGT distribution, M. stadtmanae showed an extended range of GDD structures with up to two cyclopentane ring systems. Our results thus indicate that both methanogenic and hyperthermophilic Euryarchaeota may represent source organisms of GTGT-0, GDDs and methylated-GDGTs in natural environments. All the latter components have recently been reported to be ubiquitously distributed in marine sediments but their biological origin is largely unknown. Moreover, a suite of unsaturated GDGTs without a cyclopentane moiety and up to four double bonds in the hyperthermophile T. kodakarensis was tentatively assigned