The capsular polysaccharides of Haemophilus influenzae type b and Neisseria meningitidis group C were studied for their association with outer membrane vesicles (OMV) isolated from a non capsular variant of N. meningitidis. Both the Haemophilus and meningococcal polysaccharides were treated with either phospholipase A2 to remove the fatty acid in sn-2 position or phospholipase D to remove the entire phosphoglycerol moiety. NMR of the native, phospholipase A2 and D treated polysaccharides revealed no differences in the structures between native and phospholipase A2 treated polysaccharides revealed with the phospholipase A2 treatment, the fatty acid at the sn-2 position was removed. Treatment with phospholipase D resulted in negligible fatty acid content. Treatment with either phospholipase resulted in the elimination of association with OMV>. From these results, it was clear that removal of the fatty acid in the sn-2 position was sufficient to eliminate the association of both the polysaccharides with isolated membranes. Perhaps the polysaccharide is attached to the membrane through the fatty acid in the sn-2 position.
