Evidence for the structural heterogeneity of the polysaccharide component of Coxiella burnetii strain Nine Mile lipopolysaccharide

Abstract

Highly purified lipopolysaccharide (LPS) preparation obtained from Coxiella burnetii strain Nine Mile in phase I was used to determine the structure and monosaccharide composition of the polysaccharide component. The procedure included sodium dodecyl sulphate-polyacrylamide gel electrophoresis followed by silver staining and gel chromatographic fractionation of acetic acid-hydrolyzed LPS. Five fractions (A-E) were analysed by GLC-mass spectrometry. D-Mannose and D-glycero-D-mannoheptose were present in an appreciable amount in all polysaccharide fractions (A-D), whereas the virenose and dihydrohydroxystreptose contents varied. The highest content of both rhamnose and ribose was found in the low-molecular weight polysaccharide fraction D. The former sugar is being reported for the first time to be a LPS constituent. D-Xylose and D-glucose content varied considerably in the individual fractions and was the highest in fraction A. Glucosamine and galactosaminuronic acid were present in all polysaccharide fractions and, surprisingly, L-glycero-D-mannoheptose was also found, but its presence was limited within the certain degree of polymerisation of the polysaccharide chains. Mild acid hydrolysis of LPS resulted in a partial release of dihydrohydroxystreptose and virenose residues, which were collected and identified in fraction E. The data presented indicate a strong microheterogenity within the individual polysaccharide chains with respect to their sugar composition, size, and shape. Thus, the chemical structure of Coxiella LPS appears to represent a significant departure from the structures described for enteric LPSs.