title: Lipopolysaccharide O-antigen expression and the effect of its absence on virulence in rfb mutants of Vibrio cholerae O1.
abstract: Using defined rfb mutants, defective in the biosynthesis of the O-antigen of the lipopolysaccharide (LPS), and monoclonal antibodies (MAbs) to the A, B and C LPS antigens, we have examined the distribution of the antigens and the effects of their loss. By immunogold electron microscopy, it has been possible to determine the relative amounts of the A, B and C antigens on Inaba and Ogawa cells, confirming previous studies based upon bacterial agglutination and hemagglutination inhibitions. These antigens are absent from rfb::Tn mutants selected as resistant to phages which have been shown to use the O-antigen as their receptor. These mutants were severely attenuated as measured by both LD50 and their ability to compete with the wild-type parents when analyzed in the infant mouse cholera model. These mutants were unchanged in the export of cholera toxin or other secreted proteins but revealed an altered outer membrane protein profile. The competition defect suggested an effect on TCP (toxin-coregulated pilus). An analysis of the rfb::Tn mutants revealed that they were unable to assemble TCP on their surface, but the major subunit, TcpA, could be found as an intracellular pool. These mutants could be complemented back to wild-type using the cloned rfb region, implying that functional TCP assembly is dependent upon an intact LPS.
authors.affiliation: Department of Microbiology and Immunology, The University of Adelaide, S.A., Australia.
authors.forename: J R
authors.initials: JR
authors.lastname: Iredell
authors.forename: U H
authors.initials: UH
authors.lastname: Stroeher
authors.forename: H M
authors.initials: HM
authors.lastname: Ward
authors.forename: P A
authors.initials: PA
authors.lastname: Manning
mesh_terms: D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000096:biosynthesis / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics*; D015139:Blotting, Southern; D015153:Blotting, Western; D002458:Cell Fractionation; D002771:Cholera / Q000276:immunology / Q000382:microbiology; D004251:DNA Transposable Elements; D004591:Electrophoresis, Polyacrylamide Gel; D036781:Fimbriae Proteins; D010861:Fimbriae, Bacterial / Q000378:metabolism / Q000648:ultrastructure; D015964:Gene Expression Regulation, Bacterial; D006384:Hemagglutination; D051379:Mice; D008854:Microscopy, Electron; D016254:Mutagenesis, Insertional; D019081:O Antigens / Q000096:biosynthesis / Q000737:chemistry / Q000276:immunology*; D016133:Polymerase Chain Reaction; D014734:Vibrio cholerae / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000472:pathogenicity*; D014774:Virulence
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D019081:O Antigens; C085807:TcpA protein, Vibrio cholerae; C079397:rfb protein, Bacteria; D036781:Fimbriae Proteins