Lipopolysaccharides of two strains of the phototrophic bacterium Rhodopseudomonas capsulata

Abstract

The lipopolysaccharides of Rhodopseudomonas capsulata strains St. Louis (ATCC 23782) and Sp 11 both contain l-acofriose, rhamnose, glucose and glucosamine as the main sugar constituents. 2-Keto-3-deoxyoctonate and neuraminic acid were tentatively identified. The fatty acid spectrum found with both strains comprises 3-OH−C₁₀ and C₁₂:1 (ester-linked) and 3-oxo-C₁₄ (amide-linked). Isolated lipid A from strain Sp 11 contains glucosamine, glucosamine-phosphate and the total of the fatty acids of the lipopolysaccharide. Methylation analysis of the degraded polysaccharide of this lipopolysaccharide shows l-acofriose in both terminal and 1→2 chain-linked positions in a 1:4 molar ratio. Rhamnose is exclusively chain-linked (1→2), glucose is both terminally and chain-linked (1→6) in a 1:1 molar ratio. The serological activity of the lipopolysaccharide of both the R. capsulata strains is low in antisera against living or heat-killed cells when tested by passive hemagglutination, Ouchterlony immunoprecipitation or gel-immunoelectrophoresis. No crossreaction was observed among the lipopolysaccharides of R. capsulata strains St. Louis, Sp 11 and 37b4 in immunoprecipitation. Lipopolysaccharide of strain Sp 11 was found to lack lethal toxicity in galactosamine-sensitized mice.