Abstract
Aeromonas species are found in the aquatic environment, drinking water, bottled mineral water, and different types of foods, such as meat, fish, seafood, or vegetables. Some of these species are primary or opportunistic pathogens for invertebrates and vertebrates, including humans. Among the pathogenic factors associated with these species, there are the lipopolysaccharides (LPSs). LPSs are the major components of the external leaflet of Gram-negative bacterial outer membrane. LPS is a glycoconjugate, generally composed of three portions: lipid A, core oligosaccharide, and O-specific polysaccharide or O-antigen. The latter, which may be present (smooth LPS) or not (rough LPS), is the most exposed part of the LPS and is involved in the pathogenicity by protecting infecting bacteria from serum complement killing and phagocytosis. The O-antigen is a polymer of repeating oligosaccharide units with high structural variability, particularly the terminal sugar, that confers the immunological specificity to the O-antigen. In this study, we established the structure of the O-chain repeating unit of the LPS from Aeromonas bivalvium strain 868 ET (=CECT 7113T = LMG 23376T), a mesophilic bacterium isolated from cockles (Cardium sp.) and obtained from a retail market in Barcelona (Spain), whose biosynthesis core LPS cluster does not contain the waaE gene as most of Aeromonas species. After mild acid hydrolysis, the lipid A was removed by centrifugation and the obtained polysaccharide was fully characterized by chemical analysis and NMR spectroscopy. The polymer consists of a heptasaccharide repeating unit containing D-GalNAc, L-Rha, D-GlcNAc, and D-FucNAc residues.
Highlights
The genus Aeromonas belongs to the Aeromonadaceae family and comprises Gramnegative bacteria widely distributed in aquatic environments [1]
Aeromonas bivalvium strain 868 ET (=CECT 7113T = LMG 23376T ) [13] was grown on tryptic soy broth (TSB) at 30 ◦ C and the LPS was extracted from the cells as reported in the experimental section
In this paper we reported the isolation of the LPS and the structural characterization of the O-chain from Aeromonas bivalvium strain 868 ET
Summary
The genus Aeromonas belongs to the Aeromonadaceae family and comprises Gramnegative bacteria widely distributed in aquatic environments [1] They are rod-shaped and facultative anaerobic bacteria with an optimal growth temperature range between 22 ◦ C and 37 ◦ C. Based on the latter parameter, Aeromonas spp. were divided into two major groups: mesophiles and psychrophiles [2]. They are considered emerging pathogens especially in mammals and fish. Their pathogenesis depends on a wide range of virulence factors, such as the type III secretion system, polar and lateral flagella, and the surface components of the outer membrane (i.e., the S-layer, the capsular polysaccharide, and the lipopolysaccharide) [3,4]
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