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The A. salmonicida A450 LPS O-antigen, encoded by the wbsalmo gene cluster, is exported through an ABC-2 transporter-dependent pathway. It represents the first example of an O-antigen LPS polysaccharide with three different monosaccharides in their repeating unit assembled by this pathway. Until now, only repeating units with one or two different monosaccharides have been described. Functional genomic analysis of this wbsalmo region is mostly in agreement with the LPS O-antigen structure of acetylated l-rhamnose (Rha), d-glucose (Glc), and 2-amino-2-deoxy-d-mannose (ManN). Between genes of the wbsalmo we found the genes responsible for the biosynthesis and assembly of the S-layer (named A-layer in these strains). Through comparative genomic analysis and in-frame deletions of some of the genes, we concluded that all the A. salmonicida typical and atypical strains, other than A. salmonicida subsp. pectinolytica strains, shared the same wbsalmo and presence of A-layer. A. salmonicida subsp. pectinolytica strains lack wbsalmo and A-layer, two major virulence factors, and this could be the reason they are the only ones not found as fish pathogens.

lipopolysaccharide O-antigen, 2-amino-2-deoxy-D-mannose, genomics, Aeromonas salmonicida, subspecies, Proteomics, A-surface layer

Publication DOI: 10.3390/md13063791
Journal NLM ID: 101213729
Publisher: Basel, Switzerland: Molecular Diversity Preservation International
Correspondence: elenademendoza

hotmail.com (E.M.); jtomas

ub.edu (J.M.T.); rcanals

gmail.com
Institutions: Institute of Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, UK, Department of Microbiology, Faculty of Biology, University of Barcelona, Diagonal 643, Barcelona 08071, Spain
Methods: methylation, PCR, SDS-PAGE, sugar analysis, DNA techniques, GLC, mild acid hydrolysis, de-O-acetylation, genetic methods, bioinformatic analysis, LC-ESI-MS

Initial hydridization tests using Aeromonas salmonicida typical and atypical strains showed the possibility of different lipopolysaccharide (LPS) outer cores among these strains. By chemical structural analysis, LPS-core SDS-PAGE gel migration, and functional and comparative genomics we demonstrated that typical A. salmonicida (subsp. salmonicida) strains and atypical subsp. masoucida and probably smithia strains showed the same LPS outer core. A. salmonicida subsp. achromogenes strains show a similar LPS outer core but lack one of the most external residues (a galactose linked α1-6 to heptose), not affecting the O-antigen LPS linkage. A. salmonicida subsp. pectinolytica strains show a rather changed LPS outer core, which is identical to the LPS outer core from the majority of the A. hydrophila strains studied by genomic analyses. The LPS inner core in all tested A. salmonicida strains, typical and atypical, is well-conserved. Furthermore, the LPS inner core seems to be conserved in all the Aeromonas (psychrophilic or mesophilic) strains studied by genomic analyses.

lipopolysaccharide core, genomics, Aeromonas salmonicida, inner and outer core chemical structure, typical and atypical

NCBI PubMed ID: 26904002
Publication DOI: 10.3389/fmicb.2016.00125
Journal NLM ID: 101548977
Publisher: Lausanne: Frontiers Research Foundation
Correspondence: jtomas

ub.edu (Juan M. Tomas)
Institutions: Departamento de Microbiología, Facultad de Biología, Universidad de Barcelona Barcelona, Spain
Methods: methylation, PCR, SDS-PAGE, sugar analysis, DNA techniques, GLC, MALDI-TOF MS, genetic methods, bioinformatic analysis, SDS-Tricine-PAGE