Aeromonas hydrophila Flagella Glycosylation: Involvement of a Lipid Carrier

Susana Merino,Juan M Tomás,Raquel Molero,Markus Wilhelms,Kelly M Fulton,Susan M Twine

doi:10.1371/journal.pone.0089630

Susana Merino, Juan M Tomás + Show 4 more

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https://doi.org/10.1371/journal.pone.0089630

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Abstract

Polar flagellin proteins from Aeromonas hydrophila strain AH-3 (serotype O34) were found to be O-glycosylated with a heterogeneous glycan. Mutants unable to produce WecP or Gne enzymes showed altered motility, and the study of their polar flagellin glycosylation showed that the patterns of glycosylation differed from that observed with wild type polar flagellin. This suggested the involvement of a lipid carrier in glycosylation. A gene coding for an enzyme linking sugar to a lipid carrier was identified in strain AH-3 (WecX) and subsequent mutation abolished completely motility, flagella production by EM, and flagellin glycosylation. This is the first report of a lipid carrier involved in flagella O-glycosylation. A molecular model has been proposed. The results obtained suggested that the N-acetylhexosamines are N-acetylgalactosamines and that the heptasaccharide is completely independent of the O34-antigen lipopolysaccharide. Furthermore, by comparing the mutants with differing degrees of polar flagellin glycosylation, we established their importance in A. hydrophila flagella formation and motility.

Highlights

Mesophilic Aeromonas are ubiquitous water-borne bacteria, considered opportunistic pathogens of both aquatic and terrestrial animals, some species being associated with gastrointestinal and extraintestinal human diseases [1]
WecP is the enzyme codified by a gene in the O34-antigen LPS cluster linking UDP-GalNAc to the undecaprenyl phosphate (Und-P) [6], while Gne is the enzyme able to 4-epimerize UDP-GlcNAc to UDP-GalNAc [19] codified outside the O34-antigen LPS cluster by a gene alone between non related genes codifying for a ferredoxin oxidoreductase and a protein-disulfide isomerase
We show that flagellin glycosylation impacts the ability of A. hydrophilla AH-3 to form full flagellar filaments and motility

Summary

Introduction

Mesophilic Aeromonas are ubiquitous water-borne bacteria, considered opportunistic pathogens of both aquatic and terrestrial animals, some species being associated with gastrointestinal and extraintestinal human diseases [1] These bacteria constitutively express a single polar flagellum, about 60% of strains most commonly associated with diarrhoea [2] are able to express many lateral flagella when grown in viscous environments or on surfaces [3]. Campylobacter jejuni is a bacterium with a well-characterized N-glycosylation general pathway with a heptasaccharide built through a lipid carrier undecaprenyl phosphate (Und-P) [7] In addition to this general protein glycosylation pathway C. jejuni shows O-linked glycans modifying their flagellins, with more simple glycans never built through Und-P [7]. A similar situation is observed in Helicobacter pylori [7]

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