On the revised structure of the major phospholipid of Halobacterium salinarium

Recent fast atom bombardment-mass spectrometry (FABMS) studies (Tsujimoto, K., Yorimitsu, S., Takahashi, T. and Ohashi, M. (1989) J. Chem. Commun. 668-670; Frederickson, H.L., De Leeuw, J.W., Tas, A.C., Van der Greef, J., LaVos, G.F. and Boon, J.J. (1989) Biomed. Environ. Mass. Spectrom. 18, 96-105; Kloppel, K.D. and Fredrickson, H.L. (1991) J. Chromatogr. 562, 369-376) have indicated that the structure of the major phospholipid of Halobacterium salinarium (formerly Halobacterium cutirubrum) is not 2,3-diphytanyl-sn-glycerol-1-phospho-3'-sn-glycerol-1'- phosphate (PGP), but the monomethylated derivative, 2,3-diphytanyl-sn-glycerol-1-phospho-3'-sn-glycerol-1'-methylphosphate (PGP-Me). We have now confirmed the structure of the major phospholipid of extremely halophilic archaebacteria as being this methylated structure (PGP-Me) by 1H- and 13C-NMR, FABMS and TLC of the native phospholipid and its product of mild acid hydrolysis PGP. The methylated structure (PGP-Me), rather than PGP itself, is also the major phospholipid in species of other genera of extreme halophiles examined so far, such as, Haloferax, Haloarcula, Halococcus, Natronobacterium and Natronococcus.