Bacteria belonging to the genus Aeromonas are Gram-negative mesophilic and essentially ubiquitous in the microbial biosphere; moreover they are considered very important pathogens in fish and responsible for a great variety of human infections. The virulence of Gram-negative bacteria is often associated with the structure of lipopolysaccharides, which consist of three regions covalently linked: the glycolipid (lipid A), the oligosaccharide region (core region) and the O-specific polysaccharide (O-chain, O-antigen). The O-chain region seems to play an important role in host-pathogen interaction. In the case of Aeromonas hydrophila the majority of pathogenic strains belongs to serogroups O:11, O:16, O:18 and O:34. In this paper, we report the complete structure of the O-chain of A. hydrophila strain A19 (serogroup O:14), a pathogenic strain isolated from European eels, which showed high virulence when tested in trout or mice. Dried cells were extracted by the PCP (phenol/chloroform/petroleum ether) method obtaining the lipopolysaccharide. After mild acid hydrolysis the lipid A was removed by centrifugation and the obtained polysaccharide was fully characterized by means of chemical analysis and one- and two-dimensional NMR spectroscopy. All the data collected are directed towards the following structure: (formula: see text).

Lipopolysaccharide, NMR spectroscopy, structure elucidation, Aeromonas

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
4	aLRhap	101.7	68.0	76.6	71.4	70.2	17.8
2	aDGlcp	97.8	72.4	74.0	70.6	73.1	61.6
	aDGlcp	93.6	77.1	71.2	78.3	71.8	60.9


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
4	aLRhap	4.94	4.20	3.82	3.58	4.08	1.28
2	aDGlcp	5.12	3.59	3.78	3.46	3.96	3.80-3.85
	aDGlcp	5.28	3.72	3.98	3.67	4.08	3.72


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
4	aLRhap	101.7/4.94	68.0/4.20	76.6/3.82	71.4/3.58	70.2/4.08	17.8/1.28
2	aDGlcp	97.8/5.12	72.4/3.59	74.0/3.78	70.6/3.46	73.1/3.96	61.6/3.80-3.85
	aDGlcp	93.6/5.28	77.1/3.72	71.2/3.98	78.3/3.67	71.8/4.08	60.9/3.72

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

*O[C@@H]1[C@@H](O)[C@H](C)O[C@@H](O[C@@H]2[C@@H](CO)O[C@H](*)[C@H](O[C@H]3O[C@H](CO)[C@@H](O)[C@H](O)[C@H]3O)[C@H]2O)[C@@H]1O

470.424 g/mol (C₁₈H₃₀R₂O₁₄, R = next and previous repeats, not counted in mol weight)