The lipids of Halobacterium marismortui, an extremely halophilic bacterium in the Dead Sea

Abstract

The lipids of an extremely halophilic bacterium, Halobacterium marismortui, isolated from the Dead Sea, were found to contain 86% polar lipids and 14% non-polar lipids. Four major polar lipids were detected, all derivatives of 2,3-di-O-phytanyl-sn-glycerol: (1) a novel glycolipid, 2,3-di-O-phytanyl-1-O-[beta-D-glucopyranosyl-(1'-6')-O-alpha-D-mannopyranosyl-( 1'-2')-O-alpha-D-glucopyranosyl]-sn-glycerol (11 mol%); (2) phosphatidylglycerol (11 mol%); (3) phosphatidylglycerophosphate (62 mol%); (4) phosphatidylglycerosulfate (17 mol%). In addition, a minor glycolipid (less than 1 mol%) was detected and partially characterized. Trace levels of two other unidentified glycolipids and of two unidentified phospholipids were also detected. In contrast to Halobacterium cutirubrum and H. halobium, H. marismortui did not contain any detectable sulfated glycolipid but appeared to compensate for this deficit in sulfate by having a high content of phosphatidylglycerosulfate compared to that in H. cutirubrum. The number of negative changes per mol ionic lipid appeared to be about the same for both halophiles. The non-polar lipids in H. marismortui consisted mostly of squalenes, vitamin MK-8 and bacterioruberins with traces of beta-carotene, lycopene and retinal, as in H. cutirubrum.