Hydroxyarchaetidylserine and hydroxyarchaetidyl- myo-inositol in Methanosarcina barkeri: polar lipids with a new ether core portion

Abstract

Lipids of the methanogenic archaebacterium, Methanosarcina barkeri were analyzed. The lipid content was 5.4% of dry cell and polar lipids comprised 87% of the total lipid. Polar lipids were separated into 14 spots by two-dimensional thin-layer chromatography. These were six phospholipids, seven aminophospholipids and one glycolipid, of which two phospholipids and two aminophospholipids were major constituents. After removal of polar head groups from total lipids, two kinds of glycerol diether core lipids were found. One was 2,3-di- O-phytanyl- sn-glycerol (archaeol) and the other 2- O-(3′-hydroxy-3′, 7′, 11′, 15′-tetramethyl)hexadecyl-3- O-phytanyl- sn-glycerol (hydroxyarhaeol). Those structures were identified on the basis of chemical analysis, fast atom bombardment-mass spectrometry, gas-liquid chromatography-mass spectrometry and 1H- and 13C-NMR spectrometry. The latter was a new core lipid which was different from hydroxyarchaeol of Methanothrix concilii. The hydroxyarchaeol core lipid comprised 60% of polar lipid in M. barkeri. The structures of core lipids are quite different from those previously reported by De Rosa et al. (Biochim. Biophys. Acta (1986) 875, 487–492) concerning M. barkeri lippids. The structures of two major polar lipids, both of which had hydroxyarchaeol as core portions, were elucidated. These lipids were 2- O-(3′-hydroxy)phytanyl-3- O-phytanyl- sn-glycero-1-phosephoserine (hydroxyarchaetidylserine) and 2- O-(3′-hydroxy)phytanyl-3- O-phytanyl- sn-glycero-1-phospho- myo-inositol (hydroxyarchaetidyl- myo-inositol). Archaetidylserine and archaetidylinositol, which had the usual archaeol core portion, were also present as minor polar lipids.