Archaeal phospholipids: Structural properties and biosynthesis

Abstract

Phospholipids are major components of the cellular membranes present in all living organisms. They typically form a lipid bilayer that embroiders the cell or cellular organelles, constitute a barrier for ions and small solutes and form a matrix that supports the function of membrane proteins. The chemical composition of the membrane phospholipids present in the two prokaryotic domains Archaea and Bacteria are vastly different. Archaeal lipids are composed of highly-methylated isoprenoid chains that are ether-linked to a glycerol-1-phosphate backbone while bacterial phospholipids consist of straight fatty acids bound by ester bonds to the enantiomeric glycerol-3-phosphate backbone. The chemical structure of the archaeal lipids and their compositional diversity ensures the required stability at extreme environmental conditions as many archaea thrive at such conditions including high or low temperature, high salinity and extreme acidic or alkaline pH values. However, not all archaea are extremophiles, and the presence of ether-linked phospholipids is a phylogenetic marker that distinguishes Archaea from other life forms. During the past decade, our understanding of the biosynthesis of archaeal lipids has progressed resulting in the characterization of the main biosynthetic steps of the pathway including the reconstitution of lipid biosynthesis in vitro. Here we describe the chemical and physical properties of archaeal lipids and membranes derived thereof, summarize the existing knowledge about the enzymology of the archaeal lipid biosynthetic pathway and discuss evolutionary theories associated with the "Lipid Divide" that resulted in the differentiation of bacterial and archaeal organisms. This article is part of a Special Issue entitled: Bacterial Lipids edited by Russell E. Bishop.

Complex origins of chloroplast membranes with photosynthetic machineries: multiple transfers of genes from divergent organisms at different times or a single endosymbiotic event?

“…Archaea do not use acyl lipids and have no ability of fatty acid synthesis (for a review, see Caforio and Driessen 2016). Early eukaryotes were obliged to make their membranes by obtaining fatty acids from bacterial preys.…”

Modifying Post‐Translational Modifications: A Strategy Used by Archaea for Adapting to Changing Environments?

“…[8,9] Moreover, instead of the lipid bilayer membrane architecture adopted by the majority of organisms across evolution, thermophilic archaea can synthesize tetraether lipids and assemble these into a monolayer structure as a strategy to reduce membrane fluidity at elevated temperatures. [10] Liposomes prepared from such lipids also showed lower proton permeability at elevated temperatures than did their counterparts prepared from bacterial diester-based lipids. [11] In addition, modulation of the numbers of cyclopentane rings found in the hydrocarbon chains of tetraether lipids as a function of growth temperature and pH has been reported, although the significance of such adaptations is not yet clear.…”

Evolution, Metabolism and Molecular Mechanisms Underlying Extreme Adaptation of Euryarchaeota and Its Biotechnological Potential

“…In the orders, Thermococcales and Methanobacteriales, both type of lipids, archaeal and GDGT, are present. Furthermore, in hyperthermophilic Euryarchaeota such as Thermococcales and Thermoplasmatales, GDGT with cyclic structures can be found (Table 1) [38,43].…”

“…Their phospholipid composition mainly includes long chains of methylated isoprenoids attached to a glycerol-1-phosphate molecule via an ether bond, which has been suggested to contribute to the survival in extreme environments [38]. Archaeal lipids differ in isoprenoids chain length, composition, configuration, and various modifications at the polar head groups.…”