LIPIDS OF EXTREMELY HALOPHILIC ARCHAEOBACTERIA FROM SALINE ENVIRONMENTS IN INDIA - A NOVEL GLYCOLIPID IN NATRONOBACTERIUM STRAINS

Several strains of extremely halophilic archaeobacteria, both non-alkaliphilic and alkaliphilic, including Halobacterium, Haloferax and Natronobacterium species, were isolated from salt locales in India. The major phospholipids in these strains were the C-20-C-20-glycerol diether analogues of phosphatidylglycerolmethylphosphate (PCP-Me), phosphatidylglycerol (PG) and phosphatidic acid (PA). In addition, the Halobacterium strains possessed the characteristic glycolipids, sulfated triglycosyl and tetraglycosyl diethers (S-TGD-1 and S-TeGD, respectively) and the unsulfated triglycosyl diether (TGD-1); and the Haloferax strains had the characteristic sulfated and unsulfated diglycosyl glycerol diethers (S-DCD-1 and DGD-1, respectively). The PGP-Me, and PC components of the haloalkaliphiles each occurred as two molecular species with C-20-C-20- and C-20-C-25- (isopranoid) glycerol diether lipid cores. In contrast to previous reports of the absence of glycolipids in natronobacteria, the Natronobacterium strains from India were found to contain small amounts of a novel glycolipid identified as glucopyranosyl-1 --> 6-glucopyranosyl-1 --> 1-glycerol diether (DCD-4). The lipid cores of DCD-4 also contained mainly unhydroxylated or hydroxylated C-20-C-20, C-20-C-25 and C-25-C-25 molecular species with unsaturated (isoprenoid) chains. Hydroxylated lipid cores have previously been identified only in some methanogenic archaeobacteria.