Chemical structure of the carbohydrate backbone of the lipopolysaccharide from Piscirickettsia salmonis.

Elucidation of the carbohydrate backbone structure of the lipopolysaccharide (LPS) from Piscirickettsia salmonis, the etiological agent of the salmonid rickettsial septicemia, is described. Structural information was established by a combination of monosaccharide and methylation analyses of LPS, and by NMR and mass spectrometries of oligosaccharides obtained through the use of various chemical degradations of the native polymer. The following structure of the backbone sugars was determined on the basis of the combined data from these experiments: [formula see text] The presence of two consecutive residues of diacetylated pseudaminic acid (Pse5,7Ac, 5,7-diacetamido-3,5,7,9-tetradeoxy-l-glycero-l-manno-non-2-ulosonic acid) in the LPS appears to be unique among polysaccharides containing this acidic sugar. Similarly, the presence of 4-aminoarabinose (Ara4N, 4-amino-4-deoxy-l-arabinopyranose) on O-4 of the α-GlcN1P of the lipid A moiety is a unique feature of this LPS.