Lipid Composition and Biosynthesis in Archaeal Membranes

Archaeal cell membranes are distinguished by ether-linked isoprenoid chains attached to a glycerol-1-phosphate backbone, forming either diether lipids (archaeols) or membrane-spanning tetraethers (GDGTs and GMGTs). This unique architecture yields monolayers with exceptional chemical stability and low permeability, enabling survival in extreme environments of temperature, pH and salinity. Biosynthesis initiates with formation of isoprenoid precursors via the mevalonate pathway, followed by successive ether bond constructions to glycerol phosphate. Cyclisation and head-group modifications further tune membrane fluidity and barrier function. The structural diversity of archaeal lipids underpins their roles in environmental adaptation, biogeochemical cycling and palaeoclimate proxies, while elucidation of their biosynthetic enzymes offers opportunities for bespoke lipid engineering.

Research from Nature Portfolio

Recent studies have identified a radical S-adenosylmethionine (SAM) enzyme, designated GMGT synthase (Gms), that forges the C–C linkage between isoprenoid chains to yield glycerol monoalkyl glycerol tetraethers under anaerobic conditions. Parallel work has characterised a related SAM-dependent tetraether synthase (Tes) responsible for the final cyclisation steps in GDGT assembly, demonstrating essentiality in model archaea and capacity for heterologous expression. High-resolution structural analyses of a radical SAM enzyme from a hyperthermophilic archaeon have revealed the orchestration of multiple [Fe4S4] clusters and a rubredoxin-like centre, delineating the unprecedented mechanism of sp3–sp3 carbon coupling between lipid tails.

Lipid Composition and Biosynthesis in Archaeal Membranes publication trend

The graph below shows the total number of articles in lipid composition and biosynthesis in archaeal membranes across all publications each year (not limited to Nature Index journals).

Technical terms

Ether linkage: A covalent bond between glycerol and isoprenoid chains that confers resistance to hydrolysis and thermal degradation.

Isoprenoid chain: A branched hydrocarbon polymer derived from isopentenyl pyrophosphate, forming the hydrophobic core of archaeal lipids.

Glycerol dibiphytanyl glycerol tetraether (GDGT): A membrane-spanning lipid consisting of two glycerol units linked by two C40 isoprenoid chains, forming a stable monolayer.

Glycerol monoalkyl glycerol tetraether (GMGT): A hybrid archaeal lipid featuring one glycerol moiety linked to a single isoprenoid chain and a tetraether segment, implicated in anaerobic adaptation.

Radical SAM enzyme: A class of iron-sulfur proteins that generate radical intermediates to catalyse difficult chemical transformations, such as C–C bond formation in lipid tails.

Lipid monolayer: A single-layered membrane structure formed by tetraether lipids spanning both leaflets, reducing permeability and enhancing thermostability.

References

1. Biosynthesis of GMGT lipids by a radical SAM enzyme associated with anaerobic archaea and oxygen-deficient environments. Nature Communications (2024).
2. Discovery, structure and mechanism of a tetraether lipid synthase. Nature (2022).
3. Biosynthesis of archaeal membrane ether lipids. Frontiers in Microbiology (2014).
4. Thermal Adaptation of the Archaeal and Bacterial Lipid Membranes. Archaea (2012).
5. Bridging the membrane lipid divide: bacteria of the FCB group superphylum have the potential to synthesize archaeal ether lipids. The ISME Journal: Multidisciplinary Journal of Microbial Ecology (2020).
6. Heat Stress Dictates Microbial Lipid Composition along a Thermal Gradient in Marine Sediments. Frontiers in Microbiology (2017).