Di- and Tetra-alkyl Ether Lipids of the Archaea

The Archaea represent one of the three primary kingdoms or domains of living organisms. The alternative name ‘archaebacteria’ is considered by some to be redundant. Archaea are single celled, lacking a nuclear membrane and having a low deoxyribonucleic acid content. They include thermophiles, halophiles and acidophiles, collectively termed ‘extremophiles’. Some believe that they resemble the dominant organisms in the primeval biosphere. Many of the species are methanogenic, including those found in low temperature environments. Four archaeal phyla are recognized, the Euryarchaeota, Crenarchaeota, Thaumarcheota and Korarcheota. These exist in extreme habitats, including hot springs and waters with high salt, alkali or acid conditions, but more recently it has become apparent that many such organisms exist in mild environmental conditions also, and indeed it is now suggested that these may constitute up to 20% of the oceanic biomass.