THE STRUCTURE OF THE LIPID-A COMPONENT OF RHODOCYCLUS-GELATINOSUS DR2 LIPOPOLYSACCHARIDE

Differences in lipid A and lipopolysaccharide (LPS) composition were observed between strains of sero-/ chemotype I and sero-/chemotype II of the phototrophic species Rhodocyclus gelatinosus. The lipopolysaccharides only from representative strains of sero-/chemotype I (e. g. 29/1) contained ethanolamine and ethanolamine-phosphate. In contrast, galacturonic acid was present only in strains of sero-/chemotype II. The isolated lipid A of R. gelatinosus Dr2, characterized by LD-MS and 31P-NMR, showed a composition similar to that of strain 29/1 but, in contrast, lacked ethanolamine. It is constituted of a β-1,6-glucosamine disaccharide substituted at 1 and 4′-positions by phosphomonoesters. The amino groups of the disaccharide were acylated by 3-hydroxycapric acid (3-OH-10 : 0) and these in turn were substituted by lauric or myristic acids. Hydroxyl groups at C-3 and C-3′ were esterified also by 3-hydroxycapric acid. Lipid A of R. gelatinosus strains from both sero-/chemotypes showed a high cross-reactivity with lipid A of Salmonella, both in passive hemolysis and in the hemolysis inhibition test. The ratio unsaturated/saturated fatty acids of lipid A varied depending on the growth temperature (30, 20, or 14°C). The relative amounts of unsaturated fatty acids increased at the expense of saturated fatty acids when the bacteria were grown at lower temperatures. No changes were observed with the other LPS components. © 1990, Gustav Fischer Verlag, Stuttgart · New York. All rights reserved.