Polar Lipid Structure, Composition and Biosynthesis in Extremely Halophilic Bacteria

Abstract

A review with 23 refs. The polar lipids of extremely halophilic bacteria are derived from the satd. dialkylglycerol ether, sn-2,3-diphytanylglycerol, abbreviated \"archaeol\", and consist of phospholipids (archaeol analogs of phosphatidylglycerol, PG, phosphatidylglycerophosphate, PGP, and phosphatidylglycerosulfate, PGS) and glycolipids (sulfated triglycosyl-archaeol, S-TGA-1, triglycosylarchaeol, TGA-2, sulfated diglycosyl-archaeol, S-DGA-1, and others). The polar lipid compn., particularly that of the glycolipids, appears to be correlated with the taxonomic classification of the extreme halophiles on the level of the genera so far distinguished: Halobacterium, Haloarcula, Haloferax, Halococcus, Natromobacterium and Natronococcus. Biosynthesis of these archaeol analogs of phospholipids and glycolipids proceeds by complex pathways in a multienzyme, membrane-bound system, abs. dependent on high salt concn. The first step is the alkylation of a glycerol deriv. (presumably dihydroxyacetone) with a C20-isoprenylpyrophosphate. The alkylated product, contg. ether-linked C20-isoprenyl groups, serves as precursor for both the isoprenylarchaeol phospholipids and the glycolipids. Stepwise redn. of the isoprenyl chains to phytanyl chains then gives the final satd. archaeol analogs of phospholipids and glycolipids. [on SciFinder (R)]