A hypervirulent A. hydrophila (vAh) pathotype has been identified as the etiologic agent responsible for disease outbreaks in farmed carp species and channel catfish (Ictalurus punctatus) in China and the Southeastern United States, respectively. The possible route of infection has previously been unknown; however, virulence is believed to be multifactorial, involving the production/secretion of several virulence factors, including a high molecular weight group 4 capsular polysaccharide. Here we present chemical structural evidence of a novel capsule- and LPS-associated O-antigen found present in vAh isolated during these disease outbreaks. In this study, the chemical structure of the vAh O-antigen was determined by chemical analysis, Smith degradation, mass spectrometry, and 2D proton and carbon nuclear magnetic resonance (NMR) spectroscopy and found to be unique among described bacterial O-antigens. The O-antigen consists of hexasaccharide repeating units featuring a 4)-α-l-Fucp-(1-3)-β-d-GlcpNAc-(1-4)-α-l-Fucp-(1-4)-β-d-Glcp-(1- backbone, substituted with single residue side chains of α-d-Glcp and α-d-Quip3NAc linked to O-3 of the two fucose residues. The polysaccharide is partially O-acetylated on O-6 of the 4-substituted β-Glcp residue.
Lipopolysaccharide, NMR, polysaccharide structure, Aeromonas hydrophila, Fish pathogen, O-antigen capsule
NCBI PubMed ID: 31683071Publication DOI: 10.1016/j.carres.2019.107858Journal NLM ID: 0043535Publisher: Elsevier
Correspondence: C. Heiss
Institutions: Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA, 30602, USA, Department of Biological Sciences, Auburn University, 120 West Samford Avenue, Auburn, AL, 36849, USA, Department of Biological Chemistry, University of Michigan, 1150 W. Medical Center Drive, Ann Arbor, MI, 48109, USA
Methods: 13C NMR, 1H NMR, gel filtration, NMR-2D, GC-MS, mild acid hydrolysis, GC, Smith degradation, MALDI-TOF MS, de-O-acetylation, composition analysis, SEC, HILIC
Found