Xanthomonas sinensis Cell Wall Lipopolysaccharide

Mild acid hydrolysis of the cell wall lipopolysaccharide from Xanthomonas sinensis yielded a disaccharide composed of mannose phosphate glycosidically linked to a keto-deoxy acid. Treatment of the disaccharide with alkaline phosphatase followed by α-mannosidase liberated an acid component which migrated electrophoretically with authentic 3-deoxy-d-manno-octulosonic acid (KDO), but differed chromatographically from known KDO. Molecular weight determination by mass spectrometry of the persilylated derivative of the borohydride-reduced acid yielded a value equal to that calculated for the lactone of authentic reduced KDO. Periodate oxidation followed by borohydride reduction of the Xanthomonas acid yielded two electrophoretically separable compounds. Molecular weight determinations by high resolution mass spectrometry indicated that one of these compounds had gained 2 atomic mass units, while the other had lost 100 atomic mass units from the starting material. Treatment of authentic KDO with 2% acetic acid for 90 min at 100° followed by borohydride reduction resulted in the conversion of most of the KDO into compounds identical with the reduced acids isolated from the Xanthomonas lipopolysaccharide. The results presented are consistent with the conclusion that the lipopolysaccharide occurring in the cell wall of Xanthomonas sinensis contains a single molecule of 3-deoxy-d-manno-octulosonic acid per molecule of lipopolysaccharide, and that mild acid hydrolysis of either the Xanthomonas lipopolysaccharide or of authentic KDO results in the formation of 4,7-anhydro- and 4,8-anhydro-3-deoxy-octulosonic acid.