Abstract
Chemical analyses, mass spectrometry, and NMR spectroscopy were applied to study the structure of the lipopolysaccharide (LPS) isolated from Aeromonas veronii strain Bs19, serotype O16. ESI-MS revealed that the most abundant LPS glycoforms have tetra-acylated or hexa-acylated lipid A species, consisting of a bisphosphorylated GlcN disaccharide with an AraN residue as a non-stoichiometric substituent, and a core oligosaccharide composed of Hep5Hex3HexN1Kdo1P1. Sugar and methylation analysis together with 1D and 2D 1H and 13C NMR spectroscopy were the main methods used, and revealed that the O-specific polysaccharide (OPS) of A. veronii Bs19 was built up of tetrasaccharide repeating units with the structure: →4)-α-d-Quip3NAc-(1→3)-α-l-Rhap-(1→4)-β-d-Galp-(1→3)-α-d-GalpNAc-(1→. This composition was confirmed by mass spectrometry. The charge-deconvoluted ESI FT-ICR MS recorded for the LPS preparations identified mass peaks of SR- and R-form LPS species, that differed by Δm = 698.27 u, a value corresponding to the calculated molecular mass of one OPS repeating unit (6dHexNAc6dHexHexHexNAc-H2O). Moreover, unspecific fragmentation spectra confirmed the sequence of the sugar residues in the OPS and allowed to assume that the elucidated structure also represented the biological repeating unit.
Highlights
Aeromonas spp. bacteria are widespread in aquatic environments and soil habitats and are frequently isolated from raw and processed food
We report on the chemical structure of the LPS from A. veronii strain Bs19 serologically classified as serogroup O16, which was isolated from skin of carp (Cyprinus carpio L.) with hemorrhagic and necrotic ulcers [31]
It was found that the LPS species distributed between the water and phenol phases as hydrophilic and hydrophobic fractions, in yields of 4.2% and 0.3% of the dry bacterial cell mass, respectively
Summary
Aeromonas spp. bacteria are widespread in aquatic environments and soil habitats and are frequently isolated from raw and processed food. A. veronii have been described as important fish pathogens They cause chronic disease with open dermal ulcers and other pathological lesions or acute systemic infection referred to as motile aeromonad septicemia (MAS) [5,6,7]. These bacteria, especially belonging to the species A. hydrophila, A. caviae, and A. veronii bv. The OPS variations seem to play an essential role at several stages of the infection process, including the adherence step and the ability to protect against host defense mechanisms [5] It was not clearly evidenced which structural determinants are the most important for virulence, it was found that some O serotypes are more frequently associated with certain infections. We report on the chemical structure of the LPS from A. veronii strain Bs19 serologically classified as serogroup O16, which was isolated from skin of carp (Cyprinus carpio L.) with hemorrhagic and necrotic ulcers [31]
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