Fatty acid distribution in the phospholipids of Francisella tularensis

Francisella tularensis, LVS (live vaccine strain) grown in a chemically defined medium was found to have a lipid content of 21% by dry weight. The two major phospholipids were identified as phosphatidylethanolamine (PE; 76%) and phosphatidylglycerol (PG; 24%) by thin layer chromatographic analysis, staining characteristics and quantitative chemical analyses of fatty acid, phosphate and glycerol constituents. PE contained a high proportion of 24:0 fatty acid, with lesser amounts of 24:1, 22:0 and 10:0. The major fatty acids of PG were 18:1 and 22:0. Hydroxy fatty acids, which are prominent components of F. tularensis, were conspicuously lacking in these phospholipids; it is therefore concluded that hydroxy fatty acids are constituents of other structures of the organism.