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Lipopolysaccharide (LPS) is the major glycolipid and virulence factor of Gram-negative bacteria, including Aeromonas spp. The O-specific polysaccharide (O-PS, O-chain, O-antigen), i.e., the surface-exposed part of LPS, which is a hetero- or homopolysaccharide, determines the serospecificity of bacterial strains. Here, chemical analyses, mass spectrometry, and 1H and 13C NMR spectroscopy techniques were employed to study the O-PS of Aeromonas hydrophila strain JCM 3968, serogroup O6. MALDI-TOF mass spectrometry revealed that the LPS of A. hydrophila JCM 3968 has a hexaacylated lipid A with conserved architecture of the backbone and a core oligosaccharide composed of Hep6Hex1HexN1HexNAc1Kdo1P1. To liberate the O-antigen, LPS was subjected to mild acid hydrolysis followed by gel-permeation-chromatography and revealed two O-polysaccharides that were found to contain a unique sugar 4-amino-4,6-dideoxy-l-mannose (N-acetyl-l-perosamine, l-Rhap4NAc), which may further determine the specificity of the serogroup. The first O-polysaccharide (O-PS1) was built up of trisaccharide repeating units composed of one α-d-GalpNAc and two α-l-Rhap4NAc residues, whereas the other one, O-PS2, is an α1→2 linked homopolymer of l-Rhap4NAc. The following structures of the O-polysaccharides were established: O-PS1 →3)-α-l-Rhap4NAc-(1→4)-α-d-GalpNAc-(1→3)-α-l-Rhap4NAc-(1→, O-PS2 →2)-α-l-Rhap4NAc-(1→. The present paper is the first work that reveals the occurrence of perosamine in the l-configuration as a component of bacterial O-chain polysaccharides.

O-antigen, NMR spectroscopy, O-polysaccharide, endotoxin, structure elucidation, lipopolysaccharide (LPS), MALDI-TOF mass spectrometry, Aeromonas hydrophila, L-perosamine, l-Rha4NAc

NCBI PubMed ID: 31035397
Publication DOI: 10.3390/md17050254
Journal NLM ID: 101213729
Publisher: Basel, Switzerland: Molecular Diversity Preservation International
Correspondence: aturska@hektor.umcs.lublin.pl
Institutions: Department of Genetics and Microbiology, Maria Curie-Skłodowska University in Lublin, Akademicka 19, Lublin 20-033, Poland, Department of Fish Diseases, National Veterinary Research Institute, Partyzantów 57, Puławy 24-100, Poland
Methods: 13C NMR, 1H NMR, methylation, GLC-MS, NMR-2D, SDS-PAGE, sugar analysis, GLC, MALDI-TOF MS, GPC

Amongst Aeromonas spp. strains that are pathogenic to fish in Polish aquacultures, serogroup O6 was one of the five most commonly identified immunotypes especially among carp isolates. Here, we report immunochemical studies of the lipopolysaccharide (LPS) including the O-specific polysaccharide (O-antigen) of A. veronii bv. sobria strain K557, serogroup O6, isolated from a common carp during an outbreak of motile aeromonad septicemia (MAS) on a Polish fish farm. The O-polysaccharide was obtained by mild acid degradation of the LPS and studied by chemical analyses, mass spectrometry, and 1H and 13C NMR spectroscopy. It was revealed that the O-antigen was composed of two O-polysaccharides, both containing a unique sugar 4-amino-4,6-dideoxy-L-mannose (N-acetyl-L-perosamine, L-Rhap4NAc). The following structures of the O-polysaccharides (O-PS 1 and O-PS 2) were established.

structure, O-antigen, NMR spectroscopy, O-polysaccharide, mass spectrometry, lipopolysaccharide (LPS), Aeromonas, immunospecificity, L-perosamine, Fish pathogen

NCBI PubMed ID: 31284525
Publication DOI: 10.3390/md17070399
Journal NLM ID: 101213729
Publisher: Basel, Switzerland: Molecular Diversity Preservation International
Correspondence: aturska@hektor.umcs.lublin.pl
Institutions: Department of Genetics and Microbiology, Maria Curie-Skłodowska University in Lublin, Akademicka 19, 20-033 Lublin, Poland, Laboratory of General Microbiology, Department of Biology of Bacteria, Faculty of Biology and Environmental Protection, University of Łódź, Banacha 12/16, 90-237 Łódź, Poland, Department of Fish Diseases, National Veterinary Research Institute, Partyzantów 57, 24-100 Puławy, Poland
Methods: 13C NMR, 1H NMR, methylation, GLC-MS, NMR-2D, SDS-PAGE, sugar analysis, ELISA, GLC, Western blotting, MALDI-TOF MS, serological methods, GPC

structure, O-antigen, NMR spectroscopy, O-polysaccharide, mass spectrometry, lipopolysaccharide (LPS), Aeromonas, immunospecificity, L-perosamine, Fish pathogen

Presented herein is the synthesis of the Aeromonas veronii disaccharide repeating unit which has been achieved in 11 steps starting from D-fucose and D-galactosamine.

synthesis, Gram-negative, fucose, glycosylation, GalNAc

NCBI PubMed ID: 35263695
Publication DOI: 10.1016/j.carres.2022.108530
Journal NLM ID: 0043535
Publisher: Elsevier
Correspondence: S.D. Townsend
Institutions: Department of Chemistry, Vanderbilt University, Nashville, TN, 37235, United States
Methods: 13C NMR, 1H NMR, NMR-2D, IR, TLC, chemical synthesis, glycosylation, optical rotation measurement, SEC, HR-ESI-MS