Die „freien” Lipide aus Brucella abortus Bang 4. Die Natur der Phosphatide und ihre Fettsäurezusammensetzung

Abstract

Brucella abortus Bang (strain Scherle II and strain 1119) was grown on solid media and harvested after approximately 70 h. The “free” lipids were prepared. The bacteria contained 3.3% and 4.5% free lipids by dry weight of strain Scherle II and strain 1119, respectively. The free lipids were fractionated by acetone. The acetone‐insoluble lipids (85.3% and 77.3% of the free lipids by weight of strain Scherle II and strain 1119, respectively) contained 2.85% and 3.03% P, respectively. They were analyzed by thin‐layer chromatography. The acetone‐insoluble lipids of strain Scherle II were fractionated by column chromatography on silicic acid under thin‐layer chromatographic control. Subsequently certain fractions were fractionated by further column chromatographic procedures on silicic acid and/or DEAE cellulose yielding 6 phosphatides in pure states: lecithin, phosphatidyl‐N‐dimethylethanolamine, phosphatidyl‐N‐methylethanolamine, phosphatidylethanolamine, phosphatidylglycerol and cardiolipin. These phosphatides were identified by analyses of their deacylation products. The relative amounts of these phosphatides were determined. Lecithin turned out to be the major constituent (34.5% in strain Scherle II, 37.3% in strain 1119, on a molar basis with respect to phosphorus). Strain Scherle II probably also contained phosphatidylserine and an inositol phosphatide in minor amounts. The 6 phosphatides isolated were completely susceptible to phospholipase A from snake venom. Thus, the phosphatides existed in the L‐configuration. By gas‐liquid chromatography of the fatty acids split off by the action of snake venom and of the fatty acids of the remaining lysophosphatides, we determined the positional distribution of the component fatty acids. We found C19 cyclopropane fatty acids to be located preferentially at the 2‐positions of the 6 phosphatides isolated, while the 1‐positions were preferentially occupied by different fatty acids which we tentatively determined as hydroxy acids. The lipids of Brucella abortus display an exceptional case in that they contain lecithin as their major component. In this and some other respects they resemble the lipid pattern of Agrobacterium and of certain photosynthesizing bacteria. Because of the absence of polyenoic fatty acids in bacterial lipids it is suggested that cyclopropane fatty acids play a similar role in bacterial membrane lipids as polyenoic acids do in membrane lipids of higher organisms. However, since it has been suggested that the membrane proteins have special binding sites for different apolar groups of phosphatides, it has to be supposed that the properties of bacterial membranes differ markedly from those of higher organisms. Copyright © 1968, Wiley Blackwell. All rights reserved