Identification of unusual butanetriol dialkyl glycerol tetraether and pentanetriol dialkyl glycerol tetraether lipids in marine sediments

Abstract

Butanetriol- and pentanetriol-based tetraether lipids occur in modern estuarine and deeply buried subseafloor sediments, suggesting the presence of alternative backbones in archaeal lipids.

Unusual Butane- and Pentanetriol-Based Tetraether Lipids in Methanomassiliicoccus luminyensis, a Representative of the Seventh Order of Methanogens

“…Such lipids were recently found in marine and estuarine sediments but have not previously been detected in cultured archaeal representatives (35)(36)(37). We further documented the distribution of butanetriol-based lipids in diverse marine sediments, which suggested the widespread presence of relatives of M. luminyensis.…”

“…Nevertheless, future studies on Methanomassiliicoccus BDGT and PDGT biosynthesis might help to elucidate their unresolved biochemistry. Moreover, although the identification of BDGTs and PDGTs based on HPLC-MS as well as degradation experiments by Zhu et al (36) seems conclusive, the exact structures of these unusual lipids, e.g., the stereochemistry of the butane-and pentanetriol backbone, remain to be fully resolved (e.g., by using nuclear magnetic resonance [NMR] spectroscopy). M. luminyensis further possesses a unique membrane lipid composition of mixed di-and tetraethers with glycosidic and phosphatidylglycerol head groups, which differs distinctly from all other methanogens and archaea.…”

“…Butane-and pentanetriol-based tetraether lipids have recently been identified in a number of environmental settings, such as deeply buried marine (36) and shallow estuarine (35) sediments. Meador et al (35) suggested a potential association of BDGTs with the miscellaneous crenarchaeotal group (MCG) due to the positive correlation of BDGT lipids with the relative abundance of MCG 16S rRNA sequences in microbial communities of estuarine sediments from the White Oak River, NC, USA (WOR).…”

“…Since the biosynthesis of archaeal membrane lipids typically involves dihydroxyacetone phosphate (DHAP) as an intermediate that is converted to glyc- erol-1-phosphate (G1P) (53), a different biosynthetic pathway might be required for butane-and pentanetriol-containing lipids (36). The genomes of Methanomassiliicoccales contain genes that are well known to be involved in archaeal ether lipid biosynthesis, including genes encoding homologues of G1P dehydrogenase, 3-O-geranylgeranyl-sn-glycerlyl-1-phosphate (GGGP), and digeranylgeranylglyceryl phosphate (DGGGP) synthases and four enzymes responsible for the activation of the diglyceride, the addition of polar head groups to the glycerol moiety, and the final production of archaeol via the subsequent reduction of the unsaturated isoprenoid chains (9,20).…”

Thermococcus kodakarensis modulates its polar membrane lipids and elemental composition according to growth stage and phosphate availability

“…The novel 2G-methylated GDGT (2G-Me-GDGT; IPL-14) and 2G-dimethylated GDGT (2G-diMe-GDGT; IPL-15) were identified by exact masses after Q-TOF-MS and MS/MS fragmentation patterns (Table 2; Figure 3), which were consistent with the Me-GDGT core lipids reported by Knappy et al (2009) and Knappy (2010). These methylated core lipids (i.e., 1316.3Da and 1330.4 Da, respectively) were generated via removal of the 2G headgroups after mild acid hydrolysis (Meador et al, unpublished data) and co-eluted with GDGT (1302.2 Da) during normal phase chromatography, further confirming that the additional methyl group was located in the biphytanyl chain and not in the glycerol moiety (Zhu et al, 2014). The arrangements of headgroup moieties of other IPLs were tentatively deduced from fragments obtained by MS/MS spectra (Figures 4, 5).…”