Complete Characterization of the O-Antigen from the LPS of Aeromonas bivalvium

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.

Pectobacterium and Dickeya genus—A review on structural variations of O‐polysaccharides and their role in the pathogenic process of plants

“…The uniqueness of OPSs results mainly from the presence of various monosaccharides and their different d or l configurations, numerous possibilities of glycosidic linkage, size of sugar rings as well as sequence of sugar residues in the polymer chain (Caroff & Karibian, 2003). The OPSs are most often homo‐ or hetero‐oligosaccharides composed of repeating units, which consist of two to eight monosaccharide residues (Di Guida et al, 2022). Typical monosaccharides, which exist in the pyranose form, are d ‐galactose, d ‐mannose or d ‐glucose.…”

Bacterial outer membrane vesicles and their functionalization as vehicles for bioimaging, diagnosis and therapy

“…Since OMVs contain multiple MAMPs, including LPS, lipoproteins, PG, flagellin, DNA, and RNA, it is presumable that the recognition and uptake of OMVs can engage with host PRRs to trigger innate and adaptive immune responses 42,43 oligosaccharide, and O antigen, is one of the most potent and classical PAMP 45 . The LPS binding protein delivers LPS from OMVs to CD14 on cell surfaces, where it is recognized by TLR4-MD2 complex [46][47][48] .…”

“…LPS, a large glycolipid molecule and composed of the lipid A, core oligosaccharide, and O antigen, is one of the most potent and classical PAMP. 45 The LPS binding protein delivers LPS from OMVs to CD14 on cell surfaces, where it is recognized by the TLR4–MD2 complex. 46–48 Generally, OMVs produced by E .…”

“…LPS, a large glycolipid molecule and composed of the lipid A, core oligosaccharide, and O antigen, is one of the most potent and classical PAMP. 45 The LPS binding protein delivers LPS from OMVs to CD14 on cell surfaces, where it is recognized by the TLR4-MD2 complex. [46][47][48] Generally, OMVs produced by E. coli, P. aeruginosa, and N. meningitidis contain LPS and can effectively drive TLR4 dimerization, which recruits downstream adaptor molecules to mount an inflammatory response.…”