Lipid analysis of cells and chromatophores of Rhodopseudomonas sphaeroides

The phospholipids and fatty acid analysis of four strains of Rhodopseudomonas sphaeroides and of chromatophores from two strains show some differences and also show the presence of an unusual polar neutral lipid which is ninhydrin positive and which on acid hydrolysis yields ornithine and an unidentified amino compound. This lipid is called aminolipid-X and has a fatty acid composition very different from the phospholipids. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) contain a very small amount of plasmalogen forms as determined by combined mild alkaline hydrolysis, acetic acid hydrolysis and phospholipase A₂ hydrolysis.The reaction of intact cells and chromatophores with trinitrobenzenesulfonate (TNBS), fluorodinitrobenzene (FDNB) and isethionylacetimidate (IA) show that 78% of the total PE in chromatophores is localized on the outer membrane surface. In intact cells about 15–35% of the total PE is localized on the outer surface of the plasma membrane.