Abstract
The complex lipids of Thermus aquaticus include phospholipids, glucolipids, carotenoids, and vitamin K(2) isoprenologues. The phospholipids account for 30% of the total lipids and have been identified as phosphatidylethanolamine (4%), phosphatidylglycerol (3%), phosphatidylinositol (10%), cardiolipin (3%), and phosphatidic acid (1%). The major phospholipid contained three fatty acids, a long-chain unsaturated amine, and one glycerol per phosphate and accounted for 80% of the lipid phosphate. The carotenoids accounted for 60% of the membrane lipid. The majority of the carotenoids were very polar. Mono- and diglucosyldiglyceride and the 35-, 40-, and 45-carbon vitamin K(2) isoprenologues were also identified. All these lipids were localized in the membrane of T. aquaticus. When the growth temperature was increased from 50 to 75 C and measured at 5 C intervals, there was a progressive increase in the total lipid content. The phospholipids increased 2-fold, the carotenoids increased 1.8-fold, and the glucolipids increased 4-fold between cells grown at 50 C and 75 C. The vitamin K(2) level did not change. The proportions of the individual lipids within each lipid class remained constant as the temperature of growth was raised. Metabolic studies indicated turnover of the diacyl phospholipids during pulse-chase experiments at rates comparable with mesophilic bacteria. The major phospholipid and the carotenoids did not turn over.