Structural analysis of the oligosaccharide of Histophilus somni (Haemophilus somnus) strain 2336 and identification of several lipooligosaccharide biosynthesis gene homologues.

The structure of the core oligosaccharide from a pneumonic Histophilus somni (Haemophilus somnus) strain 2336 was elucidated. The lipooligosaccharide (LOS) was subjected to a variety of degradative procedures. The structures of the purified products were established by monosaccharide and methylation analyses, NMR spectroscopy and mass spectrometry. The following structure for the core oligosaccharide was determined on the basis of the combined data from these experiments: [formula-see text]. The structural elucidation was intriguing as it suggested several differences in the LOS structures between strain 2336 and the related strain 738. Strain 738 originated following passaging of strain 2336 through a calf. The differences between the two structures are a different linkage between Gal II and GlcNAc (1-->4 here; 1-->3 in 738), the absence of phosphocholine (PCho) from 2336 and the presence of two phosphoethanolamine (PEtn) residues and Gal III (at the 2-position) of Hep II in 2336. Although pulse-field gel electrophoresis data following digest with only one restriction enzyme showed identical profiles suggesting that strains 738 and 2336 are the same strain, the structural data does suggest that, if strain 738 is indeed a phase variant of strain 2336, considerable variation occurred on calf passaging and could therefore be an intriguing example of how broadly this bacterium can adapt itself in the host.

Transferable antibiotic resistance elements in Haemophilus influenzae share a common evolutionary origin with a diverse family of syntenic genomic islands.

Transferable antibiotic resistance in Haemophilus influenzae was first detected in the early 1970s. After this, resistance spread rapidly worldwide and was shown to be transferred by a large 40- to 60-kb conjugative element. Bioinformatics analysis of the complete sequence of a typical H. influenzae conjugative resistance element, ICEHin1056, revealed the shared evolutionary origin of this element. ICEHin1056 has homology to 20 contiguous sequences in the National Center for Biotechnology Information database. Systematic comparison of these homologous sequences resulted in identification of a conserved syntenic genomic island consisting of up to 33 core genes in 16 beta- and gamma-Proteobacteria. These diverse genomic islands shared a common evolutionary origin, insert into tRNA genes, and have diverged widely, with G+C contents ranging from 40 to 70% and amino acid homologies as low as 20 to 25% for shared core genes. These core genes are likely to account for the conjugative transfer of the genomic islands and may even encode autonomous replication. Accessory gene clusters were nestled among the core genes and encode the following diverse major attributes: antibiotic, metal, and antiseptic resistance; degradation of chemicals; type IV secretion systems; two-component signaling systems; Vi antigen capsule synthesis; toxin production; and a wide range of metabolic functions. These related genomic islands include the following well-characterized structures: SPI-7, found in Salmonella enterica serovar Typhi; PAP1 or pKLC102, found in Pseudomonas aeruginosa; and the clc element, found in Pseudomonas sp. strain B13. This is the first report of a diverse family of related syntenic genomic islands with a deep evolutionary origin, and our findings challenge the view that genomic islands consist only of independently evolving modules.

Structural analysis of the lipooligosaccharide from the commensal Haemophilus somnus genome strain 129Pt.

The structure for the carbohydrate moiety of the lipooligosaccharide (LOS) from the commensal Haemophilus somnus strain 129Pt was elucidated. The structure of the core oligosaccharide and O-deacylated LOS was established by monosaccharide and methylation analyses, NMR spectroscopy and mass spectrometry. The following structure for the major fully extended carbohydrate glycoform of the LOS was determined on the basis of the combined data from these experiments. [Carbohydrate structure: see text]. In the structure Kdo is 3-deoxy-D-manno-octulosonic acid, Hep is L-glycero-D-manno-heptose and PEtn is phosphoethanolamine. Minor amounts of glycoforms containing nonstoichiometric substituents glycine and phosphate at the distal heptose residue were also identified.