The lipids of Rhodomicrobium vannielii

Abstract

Cells of Rhodomicrobium vannielii grown at 29° in a lactate-containing medium were extracted at room temperature with organic solvents. This extractable fraction contains the bulk of simple lipids (1.8% of cell dry weight) and complex lipids (phospholipids, 4.2%, and sulfolipid, 0.01%) coenzyme Q (0.09%) and pigments (carotenoids, 1.2%; and bacteriochlorophyll, 1.9%). The cell-residue contains the bound lipids (2.7%) which are liberated by treatment with alkali. The residue also contains poly-β-hydroxybutyric acid (0.2%), which was extracted with boiling CHCl3. CoQ was. determined to be Q9. Bacteriochlorophyll was found to be type a. Vaccenic acid (C18:1 ) is the major fatty acid component in both simple lipid and phospholipid fraction (ca. 90% in each fraction). The bound lipids contain many fatty acid components, including cyclopropane-, branched-, and alpha(α) and beta-(β)-hydroxy fatty acids. Seven carotenoids were found. Rhodopin (61.3% of total carotenoids by weight) and lycopene (20.5%) are the major constituents; the presence of β-carotene (3.4%) makes R. vannielii unique among the photosynthetic bacteria. The rest of the minor carotenoids are spirilloxanthin (11.2%), anhydro-rhodovibrin (1.8%), rhodovibrin (0.5%), and monodemethylated spirilloxanthin (0.5%). R. vannielii synthesizes mainly the normal spirilloxanthin series and is characterized by a high content of hydroxylated carotenoids. Crude phospholipids were separated from the bacteriochlorophyll by acetone treatment after fractionation on silicic acid columns. They were refractionated by TLC on silica gel-H and 8 components were separated; 7 of these contained phosphorus. The nature and amounts of these components were determined. They are phosphatidic acid (1.83% of total phospholipids by weight), bis-phosphatidic acid (6.75%), phosphatidyl ethanolamine (4.5%), an ornithine ester of phosphatidyl glycerol (46.5%), phosphatidyl glycerol (9.7%), an ornithine amide of an undetermined fatty acid (0.95%), phosphatidyl choline (26.5%), and the ornithine ester of lysophosphatidyl glycerol (3.2%).