Chemical Characterization of the Lipopolysaccharide of Pseudomonas solanacearum

Abstract

The carbohydrates present in lipopolysaccharide (LPS) from Pseudomonas solanacearum are rhamnose, xylose, 2-amino-2-deoxyglucose, glucose, heptose, and 2-keto-3-deoxyoctonate. LPS extracted from cultures grown on either glycerol or glucose (as the major source of carbon) and extracted after various incubation periods had similar compositions. The LPS from several strains of the bacterium contained the same component sugars, but the amounts of each sugar varied considerably. It was observed, however, that xylose and 2-amino-2-deoxyglucose increased proportionately with rhamnose, the major component. Phenol-water-extracted LPS contained measurable amounts of nucleic acid, protein, and arabinan, but none of these polymers were detected in LPS extracted with phenol-chloroform-petroleum ether. Polysaccharides liberated from LPS by mild acid hydrolysis were purified by gel filtration. Carbohydrate analysis of the LPS from a virulent, fluidal strain (K60) showed that the O-specific antigen consisted of rhamnose, xylose, and 2-amino-2-deoxyglucose in the proportions 4:1:1. The LPS of an avirulent, afluidal strain (B1) lacked the O-specific antigen; the R-core region consisted of rhamnose, glucose, heptose, and 2-keto-3-deoxyoctonate. Methylation analysis indicated that the K60 O-specific antigen was composed of a hexasaccharide repeating unit containing 3-, 2-, and 3,4-substituted rhamnopyranosyl residues, 3-substituted 2-amino-2-deoxyglucose, and terminal xylopyranose in the molar ratios 2:1:1:1:1.