Intact polar lipid distributions have become a valuable tool for the study of microbial ecosystems. In order to expand the detection and interpretation of the presence of these lipids, improved analytical methods are needed. Therefore, two high pressure liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS 2 Keywords: intact polar lipid, reversed phase, HILIC, biomarker, complex matrix ) methods, based on hydrophilic interaction chromatography (HILIC) and reversed phase (RP) chromatography were developed, taking advantage of new chromatographic possibilities such as smaller particle size and recently developed column fillings. Both were optimized to cover the broad range of compounds found in environmental samples and to cope with the associated complex sample matrices. The capabilities of the resulting methods were tested on pure standards and an environmental sample. Both methods offer improved peak resolution and detection limit, and reduced chromatographic background at twofold shorter run time compared with the previous method based on a diol column. The HILIC method offers separation according to lipid class similar to a diol column, and can thus be recommended for lipid fingerprinting. The method based on RP separation offers the unique possibility of analyzing intact polar lipids and core lipids in the same chromatographic run and an alternative mode of lipid separation based mainly on side chain structure. This method is especially suitable for separation of compounds based on side chain length, degree of saturation and/or presence of acyl/ether bonds. The combination of both newly developed chromatographic methods provides a powerful tool for the analysis of lipid distributions in environmental samples at ultra-low concentration.

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 distribution of respiratory quinone electron carriers among cultivated organisms provides clues on both the taxonomy of their producers and the redox processes these are mediating. Our study of the quinone inventories of 25 archaeal species belonging to the phyla Eury-, Cren- and Thaumarchaeota facilitates their use as chemotaxonomic markers for ecologically important archaeal clades. Saturated and monounsaturated menaquinones with six isoprenoid units forming the alkyl chain may serve as chemotaxonomic markers for Thaumarchaeota. Other diagnostic biomarkers are thiophene-bearing quinones for Sulfolobales and methanophenazines as functional quinone analogues of the Methanosarcinales. The ubiquity of saturated menaquinones in the Archaea in comparison to Bacteria suggests that these compounds may represent an ancestral and diagnostic feature of the Archaea. Overlap between quinone compositions of distinct thermophilic and halophilic archaea and bacteria may indicate lateral gene transfer. The biomarker potential of thaumarchaeal quinones was exemplarily demonstrated on a water column profile of the Black Sea. Both, thaumarchaeal quinones and membrane lipids showed similar distributions with maxima at the chemocline. Quinone distributions indicate that Thaumarchaeota dominate respiratory activity at a narrow interval in the chemocline, while they contribute only 9% to the microbial biomass at this depth, as determined by membrane lipid analysis.

16We report a new series of archaeal lipids, widespread in marine sediments and 17 tentatively assigned as isoprenoid glycerol dialkanol diethers (GDDs). These lipids are 18 structural analogues of isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) with one 19 glycerol unit missing and with each biphytanyl moiety possessing a terminal hydroxyl 20 group. The structural identification is based on molecular formulae determined from 21 accurate mass measurement and interpretation of mass spectral fragmentation patterns. 22Acetylation of GDD-0 confirmed the presence of three hydroxyl groups, and ether 23 cleavage and reduction of the products afforded two biphytanyl chains. Tests of different 24 © 2011, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/

Phase diagrams and light-scattering measurements of solutions of trimethylethyl-ammonium bromide in chloroform (~: = 4.72 at 25 C) with an ethanol content of 1 '% are reported. The system has a lower critical point near T= 25 C. The critical mole fraction is .v~ =0.0503 +0.0002, which corresponds to the reduced variables T* = 0.036 and c* = 0.029 of the restricted prhnitive model (RPM) and is slightly below the values predicted by the RPM for the critical parameters. The analysis of the scattering intensity at critical composition gives v=0.621 +0.003 for the critical exponent of the correlation length ~ with an anaplitude of ~. = 0.87 + 0.01 nm. The system, a solution of a salt of essentially spherical ions of almost equal size in a simple low-dielectric polar liquid, with critical parameters very close to predictions of the RPM, nevertheless has an lsing critical point.