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Structural studies of the cell envelope lipopolysaccharides from Haemophilus ducreyi strains ITM 2665 and ITM 4747
E K Schweda1, A C Sundström, L M Eriksson
1Clinical Research Center, Karolinska Institute, NOVUM, Huddinge Hospital, Sweden.
Abstract:
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.
Insights
Researchers elucidated the complex lipopolysaccharide structures of Haemophilus ducreyi strains, revealing distinct oligosaccharide compositions. These findings offer insights into bacterial virulence factors and potential therapeutic targets.
Area of Science:
- Microbiology
- Structural Biology
- Biochemistry
Background:
- Lipopolysaccharides (LPS) are crucial outer membrane components of Gram-negative bacteria.
- Understanding LPS structure is vital for deciphering bacterial pathogenesis and immune interactions.
- Haemophilus ducreyi is a significant human pathogen responsible for sexually transmitted infections.
Purpose of the Study:
- To determine the detailed oligosaccharide structures of lipopolysaccharides from Haemophilus ducreyi strains ITM 2665 and ITM 4747.
- To compare these structures with previously characterized LPS from other Haemophilus species.
- To explore the implications of LPS structure on bacterial virulence.
Main Methods:
- Phenol/water extraction of LPS followed by mild acid hydrolysis to obtain oligosaccharides.
- Structural elucidation using methylation analysis, fast atom bombardment-mass spectrometry (FAB-MS), and Nuclear Magnetic Resonance (NMR) spectroscopy.
- Comparative analysis with existing LPS structural data.
Main Results:
- The LPS from strain ITM 2665 contains a complex nonasaccharide core structure.
- The LPS from strain ITM 4747 features a simpler hexasaccharide core, sharing similarities with Haemophilus influenzae LPS.
- The reducing terminal 3-deoxy-D-manno-octulosonic acid (Kdo) was observed in reduced anhydro forms in both strains.
- Differences in phosphorylation of the inner core region were noted between strains.
Conclusions:
- The study successfully characterized novel LPS structures for Haemophilus ducreyi strains.
- Structural similarities between H. ducreyi and H. influenzae LPS suggest conserved biological functions.
- The findings contribute to understanding the role of LPS as a virulence factor and may inform vaccine development.