Springer Online Journal Archives 1860-2000
Summary 1. The isolation and chemical characterization of the lipopolysaccharides (O-antigens) of 12 strains of the gram-negative photosynthetic bacterium Rhodopseudomonas palustris is described. Lipopolysaccharides (LPS) were extractable with phenol/water, however, the bulk of the LPS of all strains remained in the phenol phase and only trace amounts were found in the aqueous layer. The LPS was also extractable by a phenol/chloroform/petroleum ether mixture (PCP-method), recommended for lipophilic glycolipids. Neither incubation of living bacteria with EDTA nor with NaCl liberated appreciable amounts of LPS-protein-lipid conjugates from the cells. 2. All strains investigated were found to have galactose, mannose, heptose, 2-keto-3-deoxyoctonate (KDO), glucosamine, 6-deoxy-glucosamine (quinovosamine) and a recently identified sugar, a 2,3-diamino-2,3-dideoxyhexose, as common LPS constituents. The presence of additional sugars allowed the classification of the strains into three distinct chemotypes. Chemotype I contains 4-O-methyl-D-xylose, and several non-identified amphoteric amino sugars. Chemotype II contains 4-O-methyl-D-xylose, 3-O-methyl-6-deoxy-D-talose, 6-deoxy-talose, xylose and again some unidentified amphoteric amino sugars, which were different from those of chemotype I. In chemotype III xylose, glucose, rhamnose, galactosamine and 6-O-methyl-glucosamine were identified. The main fatty acid in the high molecular weight material from the phenol phase of phenol/water extracts of all strains is β-hydroxymyristic acid. In addition in all strains β-hydroxypalmitic, palmitic and stearic acids were found. It has still to be proven that all these fatty acids are LPS constituents. 3. Like enteric LPS the LPS of R. palustris can be split by mild acid hydrolysis in a lipid portion (lipid A) and the degraded polysaccharide. But contrary to enteric lipid A, the lipid A of R. palustris does not contain glucosamine, but has the 2,3-diamino-hexose as the only amino sugar constituent. The possible occurrence of a common R-core and the question if repeating units exist in the O-specific chains of R. palustris LPS are discussed. 4. In two strains small amounts of additional LPS, which differ in their chemical composition from the respective LPS of the phenol phase, were isolated from the aqueous phase.
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