Summary auto-generated
This study characterized lipids from extremely halophilic archaeobacteria isolated from salt environments in India, including Halobacterium, Haloferax, and Natronobacterium strains. The major phospholipids in all strains were diether analogues of phosphatidylglycerolmethylphosphate (PGP-Me), phosphatidylglycerol (PG), and phosphatidic acid (PA), with varying glycerol diether chain compositions. Non-alkaliphilic Halobacterium strains contained characteristic sulfated and unsulfated glycolipids (S-TGD-1, S-TeGD, TGD-1), while Haloferax strains had sulfated and unsulfated diglycosyl diethers (S-DGD-1, DGD-1). Most significantly, Natronobacterium strains, which previously were reported to lack glycolipids, were found to contain a novel unsulfated diglycosyl glycerol diether glycolipid (DGD-4), identified as glucopyranosyl-1→6-glucopyranosyl-1→1-glycerol diether. The lipid cores of DGD-4 included saturated, unsaturated, and hydroxylated C20-C20, C20-C25, and C25-C25 molecular species. Notably, hydroxylated lipid cores had previously been identified only in methanogenic archaebacteria.
Key findings
- Natronobacterium strains from India contain a novel glycolipid (DGD-4), contradicting previous reports of absent glycolipids in natronobacteria
- DGD-4 is a diglucosyl diether with glucose units linked 1→6 to a glycerol diether core composed of saturated, unsaturated, and/or hydroxylated isoprenoid chains
- Hydroxylated lipid cores were identified in DGD-4, representing the first such identification in non-methanogenic archaebacteria
- Natronobacterium strains showed both C20-C20 and C20-C25 lipid core species, distinct from previously studied haloalkaliphiles
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Abstract
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 C20-C20-glycerol diether analogues of phosphatidylglycerolmethylphosphate (PGP-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-DGD-1 and DGD-1, respectively). The PGP- Me, and PG components of the haloalkaliphiles each occurred as two molecular species with C20-C20- and C20-C25-(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 (DGD-4). The lipid cores of DGD-4 also contained mainly unhydroxylated or hydroxylated C20-C20, C20-C25 and C25-C25 molecular species with unsaturated (isoprenoid) chains. Hydroxylated lipid cores have previously been identified only in some methanogenic archaeobacteria.