Lipids of cell walls of Pseudomonas aeruginosa and Brucella abortus

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Abstract
A survey of the content and composition of lipids from isolated cell walls of P. aeruginosa and B. abortus was made. The following results are average values from several experiments. The readily extractable lipids made up 15.7% and the firmly bound lipids 8.7% of the dry weight of the cell walls of P. aeruginosa. The readily extractable lipids of B. abortus cell walls accounted for 11.4% and the firmly bound lipids 6.4% of the dry weight of the walls. The readily extractable lipids were further separated into phospholipids, free fatty-acids, and neutral lipids. These lipids of P. peruginosa cell walls contained 44.9% phospholipids and 52.9% free fatty-acids and neutral lipids. In B. abortus cell walls, the phospholipids accounted for only 22.1% of the free lipids; whereas the free fatty-acids and neutral lipids made up 76.1%. The phospholipids of P. aeruginosa and B. abortus were shown by thin-layer chromatography to be composed of 4 and 7 components respectively. The bulk of the phospholipids was phosphatidyl ethanolamine and diphosphatidyl glycerol of the cardiolipin type. Lysophosphatidyl ethanolamine was also present in both organisms. The presence of phosphatidyl choline could not be demonstrated conclusively since choline could not be detected in the hydrolytic products of the phospholipids; however, IR spectra of the total lipids and of the phospholipids of both P aeruginosa and B. abortus showed absorption bands at 970 cm-l which are characteristic of phosphatidyl choline. Gas-liquid chromatography of the free fatty-acids of P, aeruginosa showed the major portion of these acids to be Ci6 and Ci8 saturated and monounsaturated fatty-acids. The bulk of the free-fatty-acids of B. abortus consisted of C18 saturated, monounsaturated, and polyunsaturated (C18:2) together with lesser amounts of Ci6 saturated and monounsaturated acids. Two components were tentatively identified as C19 cyclopropane and Cl9:0 fatty-acids respectively. Small amounts of both C12 and C14 saturated fatty-acids were found in both organisms. No hydroxy fatty-acids could be identified in either P. geruginosa or B. abortus. Ca and Mg, determined by atomic absorption spectrophotometry, were associated with all the phospholipid components in both organisms. However, the largest quantities of Ca and Mg were found in the phospholipid components, phosphatidyl ethanolamine and diphosphatidyl glycerol. Trace amounts of Zn were present in all phospholipid components of the cell walls of both microorganisms. Mn was not detected.

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