A novel core lipid isolated from the aceticlastic methanogen, Methanothrix concilii GP6

Abstract

The membrane lipids of Methanothrix concilii are based on two types of core lipid structures, namely, the ubiquitous 2,3-di- O-phytanyl- sn-glycerol and a second previously unidentified diether core lipid, each accounting for 70 and 30% (wt. %), respectively, of the total polar lipids. Preparation of the novel diether core lipid from either purified glycolipid-1 (GL-1) or total polar lipid in 2.5% methanolic HCl resulted in the formation of several lipid artifacts, thereby necessitating the utilization of new hydrolytic conditions. We found that mild acid hydrolysis in 0.18% methanolic HCl produced only one core lipid product from GL-1 or two core lipids from the total polar lipid fraction. This new core lipid material differed from the authentic C 20,20 diether in that it contained a hydroxyl group on C-3 of the phytanyl chain at the sn-3 position of glycerol. The full chemical designation for this novel diether is: 2- O-[3,7,11,15-tetramethyl]hexadecy l-3- O-[3′ -hydroxy-3′,7′,11′,15′-tetramethyl]hexadecyl- sn-glycerol. 1H-NMR of the total polar lipid extract could detect the presence of this new core lipid by exploiting the appearance of the methyl (C-17′) singlet at 1.24 ppm. The presence of this methyl singlet in the 1H-NMR spectrum would subsequently determine whether a strong or a mild acid hydrolysis should be used for the preparation of core lipids in methanogens.