Studies on the Biosynthesis of the O-Alkyl Bond in Glycerol Ether Lipids

ABSTRACTBacterial glycerol ether lipids (alkylglycerols) have received increasing attention during the last decades, notably due to their potential role in cell resistance or adaptation to adverse environmental conditions. Major uncertainties remain, however, regarding the origin, biosynthesis, and modes of formation of these uncommon bacterial lipids. We report here the preponderance of monoalkyl- and dialkylglycerols (1-O-alkyl-, 2-O-alkyl-, and 1,2-O-dialkylglycerols) among the hydrolyzed lipids of the marine mesophilic sulfate-reducing proteobacteriumDesulfatibacillum alkenivoransPF2803Tgrown onn-alkenes (pentadec-1-ene or hexadec-1-ene) as the sole carbon and energy source. Alkylglycerols account for one-third to two-thirds of the total cellular lipids (alkylglycerols plus acylglycerols), depending on the growth substrate, with dialkylglycerols contributing to one-fifth to two-fifths of the total ether lipids. The carbon chain distribution of the lipids ofD. alkenivoransalso depends on that of the substrate, but the chain length and methyl-branching patterns of fatty acids and monoalkyl- and dialkylglycerols are systematically congruent, supporting the idea of a biosynthetic link between the three classes of compounds. Vinyl ethers (1-alken-1′-yl-glycerols, known as plasmalogens) are not detected among the lipids of strain PF2803T. Cultures grown on different (per)deuteratedn-alkene,n-alkanol, andn-fatty acid substrates further demonstrate that saturated alkylglycerols are not formed via the reduction of hypothetic alken-1′-yl intermediates. Our results support an unprecedented biosynthetic pathway to monoalkyl/monoacyl- and dialkylglycerols in anaerobic bacteria and suggest thatn-alkyl compounds present in the environment can serve as the substrates for supplying the building blocks of ether phospholipids of heterotrophic bacteria.

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Polar and neutral isopranyl glycerol ether lipids as biomarkers of archaea in near-surface sediments from the Nankai Trough

Organic Geochemistry ◽

10.1016/j.orggeochem.2006.09.002 ◽

2006 ◽

Vol 37 (12) ◽

pp. 1643-1654 ◽

Cited By ~ 49

Author(s):

Masahiro Oba ◽

Susumu Sakata ◽

Urumu Tsunogai

Keyword(s):

Surface Sediments ◽

Nankai Trough ◽

Ether Lipids ◽

Glycerol Ether ◽

Near Surface

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The origins and implications of glycerol ether lipids in China coastal wetland sediments

Scientific Reports ◽

10.1038/s41598-019-55104-y ◽

2019 ◽

Vol 9 (1) ◽

Author(s):

Xiaoxia Lü ◽

Xiaolei Liu ◽

Changgui Xu ◽

Jinming Song ◽

Xuegang Li ◽

...

Keyword(s):

Microbial Communities ◽

Water Content ◽

Coastal Wetlands ◽

Coastal Wetland ◽

Sedimentary Environment ◽

Ether Lipid ◽

Similar Distribution ◽

Ether Lipids ◽

Glycerol Ether ◽

Reconstructed Temperature

AbstractCoastal wetlands are terrestrial-marine transition zones harboring diverse active microbial communities. The origins of diverse glycerol ether lipids preserved in coastal wetlands are rarely investigated. 16 surface sediments were collected from the coastal wetland at Guangrao (GR), Changyi (CY) and Xiamen (XM), where both climate and sedimentary environment show significant differences. Ten groups of glycerol ether lipids, including isoprenoidal and branched glycerol dialkyl glycerol tetraethers (iGDGTs and bGDGTs), isoprenoidal and branched glycerol dialkanol diethers (iGDDs and bGDDs), hydroxylated isoprenoidal GDGTs and GDDs (OH-GDGTs and OH-GDDs), overly branched GDGTs (OB-GDGTs), sparsely branched GDGTs (SB-GDGTs), hybrid isoprenoid/branched GDGTs (IB-GDGTs) and a tentatively assigned H-shaped branched GDGTs (H-B-GDGTs) were detected and quantified. Sediments collected in the north (Guangrao and Changyi) contain, in general, a lower abundance of GDGT (3.7–55.9 ng/g sed) than samples from south (Xiamen; 251–1020 ng/g sed). iGDGTs and bGDGTs are the predominant components at all sites and account for 17.2–74.3% and 16.1–75.1% of total ether lipids, respectively. The relative abundance of iGDGTs decreases but that of bGDGTs increases with the distance from sea, suggesting a marine vs. terrestrial origin of iGDGT and bGDGTs, respectively. In addition, the methylation index (MIOB/B/SB) of branched GDGTs shows a significant inverse correlation with water content, suggesting that marine waters have a major influence on the microbial communities inhabiting wetland sediment. Such an assumption was confirmed by the distinct lipid pattern of three low water content (<5%) samples collected in an area isolated from tidal flushing. The other isoprenoidal ether lipids, such as iGDDs, OH-GDGTs and OH-GDGTs, have a similar distribution as iGDGTs, indicating a common biological source, so do the corresponding non-isoprenoidal ether lipid series with bGDGTs. The BIT value increases with increasing distance from the sea, which implies that the BIT index can be probably applied to trace past sea level change in costal wetland settings. The reconstructed temperature from TEX86 shows significant offset from observed data, but only little deviation for the MBT/CBT calculated temperature. This suggests that the MBT/CBT has the potential to reconstruct past temperatures in coastal wetland settings.

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