Elucidation of the Structure and Phenotypic Properties of the Oligosaccharide from Wild Type Moraxella Bovis Epp63 Lipooligosaccharide

Moraxella bovis is the causative agent of infectious bovine kerato-conjunctivitis, a disease that causes widespread economic loss and animal welfare issues worldwide. Structural elucidation of the core oligosaccharide of the rough phenotype of Moraxella bovis strain Epp63 was undertaken using GC-MS, methylation analysis and NMR spectroscopy. The unusual features of this oligosaccharide which was found to contain 10 sugar residues in addition to 3-deoxy-D-mannooctulosonic acid (KDO) include the fact that the oligosaccharide does not contain heptose and the KDO residue is directly attached to a (→4,6)-branched glucose and the oligosaccharide contains a terminal open chain acetal-linked N-acetylgalactosamine, (1S)-GalaNAc residue →4,6-linked to a sub-terminal galactose residue. Using glycosyltransferase mutant bacteria we have also been able to identify the function of some of the glycosyltransferase enzymes important in LOS biosynthesis. Furthermore, biological evaluation of these truncated LOS mutants has provided insight into the role of the oligosaccharide.