Structural studies of the cell envelope lipopolysaccharides from Haemophilus ducreyi strains ITM 2665 and ITM 4747.

The structures of the lipopolysaccharides from Haemophilus ducreyi strains ITM 2665 and ITM 4747 have been investigated. Oligosaccharides were obtained from phenol/water-extracted lipopolysaccharide by mild acid hydrolysis and were studied with methylation analysis, fast atom bombardment-mass spectrometry, and NMR spectroscopy. The major oligosaccharide obtained from strain 2665 is a nonasaccharide with the following structure: beta-D-Galp-1-->4-beta-D-GlcNAcp-1-->3-beta-D-Galp-1-->4-D-alpha-D -Hepp- 1-->6-beta-D-Glcp-1-->(L-alpha-D-Hepp-1-->2-L-alpha-D-Hepp-1 -->3)-4-L-alpha- D-Hepp-Kdo, where the reducing terminal 3-deoxy-D-manno-octulosonic acid (or Kdo) exists in reduced anhydro forms. The proposed structure complements the preliminary structure described for Haemophilus ducreyi strain 35000 (Melaugh, W., Phillips, N. J., Campagnari, A. A., Karalus, R., and Gibson, B. W. (1992) J. Biol. Chem. 267, 13434-13439) with the missing anomeric configurations. The saccharide isolated from strain 4747 is a markedly simpler hexasaccharide with the following structure: beta-D-Galp-1-->4-beta-D-Glcp-1-->(L-alpha-D-Hepp-1-->2-L-alpha-D- Hepp- 1-->3)4-L-alpha-D-Hepp-Kdo. Apart from a different phosphorylation of the inner core region the proposed structure is identical to the structure of lipopolysaccharide from an only distantly related bacterium, viz. Haemophilus influenzae nontypable strain 2019 (Phillips, N. J., Apicella, M. A., Griffiss, J. M., and Gibson, B.W. (1992) Biochemistry 31, 4515-4526). The implications of these findings as regards the role of lipopolysaccharide as a virulence factor are discussed.