STRUCTURAL CHARACTERIZATION OF THE LIPIDS-A OF 3 BORDETELLA-BRONCHISEPTICA STRAINS - VARIABILITY OF FATTY-ACID SUBSTITUTION

The structures of lipids A isolated from the lipopolysaccharides (LPSs ; endotoxins) of three different pathogenic Bordetella bronchiseptica strains were investigated by chemical composition and methylation anal ysis, gas chromatography-mass spectrometry, nuclear magnetic resonance , and plasma desorption mass spectrometry (PDMS). The analyses reveale d that the LPSs contain the classical lipid A bisphosphorylated beta-( 1-->6)-linked D-glucosamine disaccharide with hydroxytetradecanoic aci d in amide linkages. Their structures differ from that of the lipid A of Bordetella pertussis endotoxin by the replacement of hydroxydecanoi c acid on the C-3 position with hydroxydodecanoic acid or dodecanoic a cid and the presence of variable amounts of hexadecanoic acid. The dod ecanoic acid is the first nonhydroxylated fatty acid to be found direc tly linked to a lipid A glucosamine. The lipids A were heterogeneous a nd composed of one to three major and several minor molecular species. The fatty acids in ester linkage were localized by PDMS of chemically modified lipids A. B. pertussis lipids A are usually hypoacylated wit h respect to those of enterobacterial lipids A. However, one of the th ree B. bronchiseptica strains had a major hexaacylated molecular speci es. C-4 and C-6' hydroxyl groups of the backbone disaccharide were uns ubstituted, the latter being the proposed attachment site of the polys accharide. The structural variability seen in these three lipids A was unusual for a single species and may have consequences for the pathog enicity of this Bordetella species.