Core Lipids of Hyperthermophilic Archaeon, Pyrococcus horikoshii OT3

Core lipids of the new hyperthermophilic archaeon, Pyrococcus horikoshii OT3, purified from hot sediment at the Iheya Ridge in the id-Okinawa Trough were investigated. More than 80% of core lipids in the isolate were composed of caldarchaeol (dibiphytanyldiglycerol tetraether). Archaeol (diphytanylglycerol diether) and the trialkyl type of caldarchaeol were present as minor components. A core lipid similar to that of the H form caldarchaeol found in Methanothermus fervidus was detected at a total content of 15%. The negative FAB-MS spectrum of caldarchaeol from strain OT3 showed the major molecular ionic peak (M-H)to be at m/z 1300. The isoprenoid chain of the caldarchaeol was composed primarily of a C40 hydrocarbon without cyclopentane rings. Isoprenoid chains prepared from total lipids of strain OT3 consisted of 9% C20, 82% acyclic-C40, 7% monocyclic-C40 and 2% bicyclic-C40. Tricyclic-C40 and tetracyclic-C40, observed in the order Sulfolobales of thermophilic archaea, were not found in the isolate. The core lipids from strain OT3 thus more resemble those of thermophilic methanogen in Euryarchaeota rather than those of the order, Sulfolobales in Crenarchaeota.