Intramolecular stable carbon isotopic analysis of archaeal glycosyl tetraether lipids

Abstract

Glycolipids are prominent constituents in the membranes of cells from all domains of life. For example, diglycosyl-glycerol dibiphytanyl glycerol tetraethers (2Gly-GDGTs) are associated with methanotrophic ANME-1 archaea and heterotrophic benthic archaea, two archaeal groups of global biogeochemical importance. The hydrophobic biphytane moieties of 2Gly-GDGTs from these two uncultivated archaeal groups exhibit distinct carbon isotopic compositions. To explore whether the isotopic compositions of the sugar headgroups provide additional information on the metabolism of their producers, we developed a procedure to analyze the δ(13)C values of glycosidic headgroups. Successful determination was achieved by (1) monitoring the contamination from free sugars during lipid extraction and preparation, (2) optimizing the hydrolytic conditions for glycolipids, and (3) derivatizing the resulting sugars into aldononitrile acetate derivatives, which are stable enough to withstand a subsequent column purification step. First results of δ(13)C values of sugars cleaved from 2Gly-GDGTs in two marine sediment samples, one containing predominantly ANME-1 archaea and the other benthic archaea, were obtained and compared with the δ(13)C values of the corresponding biphytanes. In both samples the dominant sugar headgroups were enriched in (13)C relative to the corresponding major biphytane. This (13)C enrichment was significantly larger in the putative major glycolipids from ANME-1 archaea (∼15‰) than in those from benthic archaea (<7‰). This method opens a new analytical window for the examination of carbon isotopic relationships between sugars and lipids in uncultivated organisms.

Carbon flow from volcanic CO2 into soil microbial communities of a wetland mofette

“…Bacterial and archaeal lipid biomarkers were extracted from 1 to 2 g (dry weight (dw)) soil from the unlabeled and 13 CO 2 incubations as described in the Supplementary Information. Fatty acid methyl esters and ether-cleaved hydrocarbons were analyzed by GC-MS for identification, GC-FID for quantification and isotope-ratio-monitoring gas chromatography/mass spectrometry for stable carbon isotopic composition (Elvert et al, 2003;Lin et al, 2010). Fatty acids are presented as the total number of carbon atoms, followed by a colon and the number of double bonds.…”

Optimizing sample pretreatment for compound-specific stable carbon isotopic analysis of amino sugars in marine sediment

“…After being converted to ANA derivatives, amino sugars extracted from the environmental samples were further purified with a self-packed silica gel column (0.5 g; Kieselgel, 0.06-0.2 mm; Carl Roth GmbH, Karlsruhe, Germany; cf. Lin et al, 2010). The best recovery (> 95 % of each amino sugar as an ANA derivative) was achieved by elution with 8 ml hexane/ethyl acetate (1 : 4, v : v).…”

“…The stable carbon isotopic composition (δ 13 C) of individual cellular biomarkers can reveal the carbon metabolism and/or lifestyles of the source organisms in natural environments (e.g., Lin et al, 2010;Schubotz et al, 2011), and incubations with 13 C-labeled substrates have been used to probe microbial communities by tracking the production of labeled biomarkers over time (e.g., Veuger et al, 2006;Kellermann et al, 2012;Lin et al, 2013). The latter technique has been widely employed in soil science to investigate the formation and/or turnover kinetics of amino sugars (e.g., Glaser et al, 2005;Decock et al, 2009;Bai et al, 2012).…”

“…The accuracy and precision of the GC-based method, though compromised by the introduction of carbon during derivatization (Glaser and Gross, 2005), has been shown to sufficiently resolve molecular isotopic differences caused by diverse biogeochemical processes in marine sediments (cf. Lin et al, 2010). Therefore, we consider GC-IRMS an attractive alternative to LC-IRMS for the isotopic analysis of amino sugars in deep marine sediments.…”

“…The δ 13 C values and the corresponding standard deviations (s Total ) of individual amino sugars were calculated following the procedure described by Glaser and Gross (2005), with a slight modification. 3-Omethyl-D-glucopyranose (3-O-Me-Glc) was applied as an internal standard to correct the isotopic fractionation that is known to occur during acetylation of the hydroxyl groups (Lin et al, 2010). A compound-specific factor F to correct for fractionation during derivatization was introduced by Glaser and Gross (2005, Eq.…”