Abstract
A group of virulent Aeromonas hydrophila, A. sobria, and A. veronii biovar sobria strains isolated from humans and fish have been described; these strains classified to serotype O11 are serologically related by their lipopolysaccharide (LPS) O-antigen (O-polysaccharide), and the presence of an S-layer consisting of multiple copies of a crystalline surface array protein with a molecular weight of 52 kDa in the form of a crystalline surface array which lies peripheral to the cell wall. A. hydrophila strain AH-1 is one of them. We isolated the LPS from this strain and determined the structure of the O-polysaccharide, which was similar to that previously described for another strain of serotype O11. The genetics of the O11-antigen showed the genes (wbO11 cluster) in two sections separated by genes involved in biosynthesis and assembly of the S-layer. The O11-antigen LPS is an example of an ABC-2-transporter-dependent pathway for O-antigen heteropolysaccharide (disaccharide) assembly. The genes involved in the biosynthesis of the LPS core (waaO11 cluster) were also identified in three different chromosome regions being nearly identical to the ones described for A. hydrophila AH-3 (serotype O34). The genetic data and preliminary chemical analysis indicated that the LPS core for strain AH-1 is identical to the one for strain AH-3.
Highlights
Lipopolysaccharides (LPS) are amphiphilic macromolecules generally comprised of three defined regions distinguished by their genetics, structures, and function: the lipid A, the core oligosaccharide (OS) and a polysaccharide portion, O-antigen
A group of virulent Aeromonas hydrophila, A. sobria, and A. veronii biovar sobria strains isolated from humans and fish have been described; these strains are serologically related by their O-antigens, and the presence of an S-layer consisting of multiple copies of a protein (VapA) with a molecular weight of 52,000 Da in the form of a crystalline surface array peripheral to the cell wall
We found genes codifying for the production and export/assembly of the S-layer characteristic from strain AH-1, between the biosynthetic genes for O11-antigen LPS production
Summary
Lipopolysaccharides (LPS) are amphiphilic macromolecules generally comprised of three defined regions distinguished by their genetics, structures, and function: the lipid A, the core oligosaccharide (OS) and a polysaccharide portion, O-antigen. While the structures of lipid A and core oligosaccharide are highly conserved among bacterial genera, the O-polysaccharide varies in common bacterial species [1]. The taxonomy of the genus Aeromonas is complex due to the continuous description of novel species and the rearrangement of strains and species described so far [2]. In the current edition of Bergey’s Manual of Systematic Bacteriology, three genera (Aeromonas, Oceanimonas and Tolumonas) are listed in this family, two more genera have been described recently, Oceanisphaera [4] and Zobellella [5]
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