Host-like carbohydrates promote bloodstream survival of Vibrio vulnificus in vivo.
Bottom Line: Here we demonstrate that sialic acid-like molecules are present on the lipopolysaccharide of V. vulnificus, are required for full motility and biofilm formation, and also contribute to the organism's natural resistance to polymyxin B.Further experiments in a murine model of intravenous V. vulnificus infection demonstrated that expression of nonulosonic acids had a striking benefit for bacterial survival during bloodstream infection and dissemination to other tissues in vivo.In fact, levels of bacterial persistence in the blood corresponded to the overall levels of these molecules expressed by V. vulnificus isolates.
Affiliation: Department of Biological Sciences, University of Delaware, Newark, Delaware, USA.Show MeSH
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Mentions: The LPS O antigen is a frequent site of NulO modification in Gram-negative organisms (16, 29–31). To investigate whether V. vulnificus LPS contains NulO residues, LPS was isolated from the WT and Δnab2 strains. Polyacrylamide gel electrophoresis followed by glycan visualization using the Pro-Q Emerald stain demonstrated a lower-molecular-weight band in the Δnab2 strains than in the WT strain (Fig. 2A), suggesting a truncation of LPS. The higher-molecular-weight band seen with WT LPS was partially restored in the Δnab2/pnab2 strain (Fig. 2A). This finding is consistent with the intermediate levels of NulO measured in the Δnab2/pnab2 complemented strain (Fig. 1C). The material used for electrophoresis was also subjected to fluorescence derivatization and HPLC analysis, verifying that NulOs were present in the LPS preparations (data not shown). In contrast, HPLC of flagellum subunits from isolated SDS-PAGE bands did not yield evidence of the presence of NulOs, despite the fact that positive controls analyzed in parallel (bacterial species known to produce glycosylated flagella) gave the expected result (data not shown). We note that a more sensitive detection method may be required to completely rule out the possibility of direct glycosylation of flagellar proteins in V. vulnificus.
Affiliation: Department of Biological Sciences, University of Delaware, Newark, Delaware, USA.