• Medientyp: E-Artikel
  • Titel: The Lipopolysaccharide of Brucella abortus BvrS/BvrR Mutants Contains Lipid A Modifications and Has Higher Affinity for Bactericidal Cationic Peptides
  • Beteiligte: Manterola, Lorea; Moriyón, Ignacio; Moreno, Edgardo; Sola-Landa, Alberto; Weiss, David S.; Koch, Michel H. J.; Howe, Jörg; Brandenburg, Klaus; López-Goñi, Ignacio
  • Quelle: Journal of Bacteriology ; 187 ( 2005 ) S. 5631-5639
  • Erschienen: American Society for Microbiology, 2005
  • Sprache: Englisch
  • DOI: 10.1128/jb.187.16.5631-5639.2005
  • ISSN: 0021-9193; 1098-5530
  • Schlagwörter: Molecular Biology ; Microbiology
  • Zusammenfassung: <jats:title>ABSTRACT</jats:title> <jats:p> The two-component BvrS/BvrR system is essential for <jats:italic>Brucella abortus</jats:italic> virulence. It was shown previously that its dysfunction abrogates expression of some major outer membrane proteins and increases bactericidal peptide sensitivity. Here, we report that BvrS/BvrR mutants have increased surface hydrophobicity and susceptibility to killing by nonimmune serum. The <jats:italic>bvrS</jats:italic> and <jats:italic>bvrR</jats:italic> mutant lipopolysaccharides (LPSs) bound more polymyxin B, chimeras constructed with <jats:italic>bvrS</jats:italic> mutant cells and parental LPS showed augmented polymyxin B resistance, and, conversely, parental cells and <jats:italic>bvrS</jats:italic> mutant LPS chimeras were more sensitive and displayed polymyxin B-characteristic outer membrane lesions, implicating LPS as being responsible for the phenotype of the BvrS/BvrR mutants. No qualitative or quantitative changes were detected in other envelope and outer membrane components examined: periplasmic β(1-2) glucans, native hapten polysaccharide, and phospholipids. The LPS of the mutants was similar to parental LPS in O-polysaccharide polymerization and fine structure but showed both increased underacylated lipid A species and higher acyl-chain fluidity that correlated with polymyxin B binding. These lipid A changes did not alter LPS cytokine induction, showing that in contrast to other gram-negative pathogens, recognition by innate immune receptors is not decreased by these changes in LPS structure. Transcription of <jats:italic>Brucella</jats:italic> genes required for incorporating long acyl chains into lipid A ( <jats:italic>acpXL</jats:italic> and <jats:italic>lpxXL</jats:italic> ) or implicated in lipid A acylation control ( <jats:italic>bacA</jats:italic> ) was not affected. We propose that in <jats:italic>Brucella</jats:italic> the outer membrane homeostasis depends on the functioning of BvrS/BvrR. Accordingly, disruption of BvrS/BvrR damages the outer membrane, thus contributing to the severe attenuation manifested by <jats:italic>bvrS</jats:italic> and <jats:italic>bvrR</jats:italic> mutants. </jats:p>
  • Beschreibung: <jats:title>ABSTRACT</jats:title>
    <jats:p>
    The two-component BvrS/BvrR system is essential for
    <jats:italic>Brucella abortus</jats:italic>
    virulence. It was shown previously that its dysfunction abrogates expression of some major outer membrane proteins and increases bactericidal peptide sensitivity. Here, we report that BvrS/BvrR mutants have increased surface hydrophobicity and susceptibility to killing by nonimmune serum. The
    <jats:italic>bvrS</jats:italic>
    and
    <jats:italic>bvrR</jats:italic>
    mutant lipopolysaccharides (LPSs) bound more polymyxin B, chimeras constructed with
    <jats:italic>bvrS</jats:italic>
    mutant cells and parental LPS showed augmented polymyxin B resistance, and, conversely, parental cells and
    <jats:italic>bvrS</jats:italic>
    mutant LPS chimeras were more sensitive and displayed polymyxin B-characteristic outer membrane lesions, implicating LPS as being responsible for the phenotype of the BvrS/BvrR mutants. No qualitative or quantitative changes were detected in other envelope and outer membrane components examined: periplasmic β(1-2) glucans, native hapten polysaccharide, and phospholipids. The LPS of the mutants was similar to parental LPS in O-polysaccharide polymerization and fine structure but showed both increased underacylated lipid A species and higher acyl-chain fluidity that correlated with polymyxin B binding. These lipid A changes did not alter LPS cytokine induction, showing that in contrast to other gram-negative pathogens, recognition by innate immune receptors is not decreased by these changes in LPS structure. Transcription of
    <jats:italic>Brucella</jats:italic>
    genes required for incorporating long acyl chains into lipid A (
    <jats:italic>acpXL</jats:italic>
    and
    <jats:italic>lpxXL</jats:italic>
    ) or implicated in lipid A acylation control (
    <jats:italic>bacA</jats:italic>
    ) was not affected. We propose that in
    <jats:italic>Brucella</jats:italic>
    the outer membrane homeostasis depends on the functioning of BvrS/BvrR. Accordingly, disruption of BvrS/BvrR damages the outer membrane, thus contributing to the severe attenuation manifested by
    <jats:italic>bvrS</jats:italic>
    and
    <jats:italic>bvrR</jats:italic>
    mutants.
    </jats:p>