Genetic modulation of Shigella flexneri 2a lipopolysaccharide O antigen modal chain length reveals that it has been optimized for virulence

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dc.contributor.authorMorona, R.
dc.contributor.authorDaniels, C.
dc.contributor.authorVan Den Bosch, L.
dc.date.issued2003
dc.descriptionThe definitive version is available at www.blackwell-synergy.com
dc.description.abstractThe lipopolysaccharide (LPS) molecules of Shigella flexneri 2a have O antigen (Oag) polysaccharides with two modal chain length distributions. The chromosomal wzzSF gene results in short (S) type Oag chains [11–17 Oag repeat units (RUs)], and the pHS-2 plasmid-located wzzpHS2 gene results in very long (VL) type Oag chains (>90 Oag RUs). S. flexneri wzzSF mutants are unable to form plaques on HeLa cell monolayers and F-actin comet tails, indicating that IcsA/ VirG function in actin-based motility (ABM) is defective. An S. flexneri wzzSF wzzpHS2 double mutant had LPS with relatively short, random length Oag chains and, paradoxically, was able to form plaques and F-actin comet tails. The influence of Oag modal chain length distribution on virulence and related properties was investigated using complementation with different wzz genes. WzzO139 from Vibrio cholerae O139 and WzzST from Salmonella enterica serovar Typhimurium were fully functional in Shigella flexneri, resulting in LPS with either very short (VS) type Oag chains (2–7 Oag RUs) or long (L) type Oag chains (19–35 RUs), respectively. In the absence of VL-type Oag chains, the VS-, S- and L-type Oag chains were permissive for plaque and F-actin comet tail formation. However, in the presence of LPS with VL-type Oag chains, the VS- and S-type Oag chains but not the L-type Oag chains were permissive for plaque and F-actin comet tail formation. These data, and the results of a previous investigation, show that IcsA function in ABM requires LPS Oag chains with at least two but less than 18 RUs when VL-type Oag chains are co-expressed on the cell surface. However, in the absence of the VL-type Oag chains, LPS Oag chains with at least two but less than 90 RUs are able to support IcsA function in ABM. Indirect immunofluorescence staining of IcsA on the cell surface of the S. flexneri strains did not correlate with the observed effect of Oag chain length on plaque and F-actin comet tail formation. However, when intracellular bacteria lacking VL-type Oag chains were examined, an inverse correlation between Oag modal chain length and detection of IcsA was observed, i.e. staining decreased with increased modal length. It is hypothesized that Oag chains can mask IcsA and interfere with its function in ABM, and a model is presented to explain how LPS Oag and IcsA may interact. It is suggested that S. flexneri 2a has evolved to synthesize LPS with two Oag modal chain lengths, as S-type Oag chains allow IcsA to function in ABM in the presence of VL-type Oag chains that confer resistance to serum.
dc.description.statementofresponsibilityRenato Morona, Craig Daniels and Luisa Van Den Bosch
dc.identifier.citationMicrobiology (United Kingdom), 2003; 149(4):925-939
dc.identifier.doi10.1099/mic.0.26141-0
dc.identifier.issn1350-0872
dc.identifier.issn1465-2080
dc.identifier.orcidMorona, R. [0000-0001-7009-7440]
dc.identifier.urihttp://hdl.handle.net/2440/3110
dc.language.isoen
dc.publisherSoc General Microbiology
dc.source.urihttp://mic.sgmjournals.org/cgi/content/abstract/149/4/925
dc.subjectCell Line
dc.subjectHela Cells
dc.subjectAnimals
dc.subjectHumans
dc.subjectGuinea Pigs
dc.subjectShigella flexneri
dc.subjectDysentery, Bacillary
dc.subjectKeratoconjunctivitis
dc.subjectActins
dc.subjectO Antigens
dc.subjectBacterial Proteins
dc.subjectDNA-Binding Proteins
dc.subjectTranscription Factors
dc.subjectFluorescent Antibody Technique
dc.subjectVirulence
dc.subjectGene Expression Regulation, Bacterial
dc.subjectMutation
dc.subjectCricetinae
dc.titleGenetic modulation of Shigella flexneri 2a lipopolysaccharide O antigen modal chain length reveals that it has been optimized for virulence
dc.typeJournal article
pubs.publication-statusPublished

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