Abstract
The lipids of the archaebacteria grown at a normal temperature is fundamentally the archaeol in which sn-2 and sn-3 of the glycerol are ether linked with the phytanol of C20, but those of the bacteria grown at high temperature are mainly the caldarchaeol with the structure in which the archaeol of two molecules confronts each hydrocarbon and methyl terminals of hydrocarbon chains are linked.
The thermophilic archaea can be separated into two types, i.e., those living in a strong acidic condition and others living around neutral condition, and also, the former consists of tetraether-type lipids without exception. In the bacteria growing in a neutral condition, however, not only the tetraether-type lipids, but also some of those being composed of the diether-type lipids as their main lipids have been detected.
Main lipids of the archaea belonging to family Sulfolobaceae possess the calditocaldarchaeol as a core lipid, which formed by substituting the glycerol of the one side of the caldarchaeol with the calditol and it seems highly probable that such characteristic structure is contributed to the acid resistance and the thermostability of these archaebacteria.
In addition, it became clear that the polar heads containing phosphorus in lipids of the thermophilic archaea consist of the negative electric charge components such as inositol phosphate.
