A unique characteristic of Archaea is the presence of ether linkages in the lipids of their cytoplasmic membranes which distinguishes archaea form eukaryotes and most bacteria. The structure of cytoplasmic membranes of many archaea is a lipid bilayer composed of glycerol diether lipids which are analogous (similar or parallel) to lipid layers of bacterial and eukaryotic membranes. The cytoplasmic membrane in the same of the archaeobacteria or archaea are monolayers made of glycerol tetraether lipids. These monolayers are heat stable with hydrophilic portions (glycerol) at the cytoplasm and external interfaces and an internal hydrophobic portion (hydrocarbons). The difference lies that bacterial and eucaryotic lipids are generally based on ester linkages. The archaeal lipids are mainly isoprany] glycerol ethers, which are synthesized by the condensation of glycerol or other alcohols with isopreroid hydrocarbons of 20, 25, or 40 carbon atoms.

Many of the archaeobacteria are extreme thermophiles and same can grow at temperature over 100°C. Some extremely thermophiles archaea are sulphate reducers and other metabolise elemental sulphur and hydrogen sulphide.

There are halophiles among archaea which grow under harsh environments as Dead Sea. Methanogens grow under anaerobic and often thermophilic condition and are the only organisms that can produce methane.

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