Variation in Molecular Species of Core Lipids from the Order Thermoplasmales Strains Depends on the Growth Temperature

The core lipids from five strains of the order Thermoplasmales grown at various temperatures have been investigated. The major core lipid of the cell membrane in these strains was caldarchaeol (2, 2′, 3, 3′-tetra-O-di(biphytanyl)-sn-diglycerol). Five types of molecular species of the C40 isoprenoid chains having different numbers of cyclopentane rings were detected in caldarchaeol. In the strains of the genus Picrophilus, a novel molecular species of the C40 isoprenoid chain, being a C40-bicyclic isomer, was detected. An increasing degree of cyclization depending on the rising growth temperatures was observed in all the strains examined.