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Brucella melitensis 16M produces a mannan and other extracellular matrix components typical of a biofilm

Marie Godefroid1, Mona V Svensson, Pierre Cambier

  • 1Unité de Recherche en Biologie Moléculaire, Facultés Universitaires Notre-Dame de la Paix, Namur, Belgium.

FEMS Immunology and Medical Microbiology
|May 26, 2010
PubMed

Insights

Overexpressing the aiiD gene in Brucella melitensis causes bacterial clumping and enhances biofilm formation. This study characterizes the exopolysaccharide involved, revealing its composition and structure.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • Brucella melitensis quorum-sensing (QS) mutations influence exopolysaccharide-containing clump formation.
  • The aiiD gene's role in QS and its impact on B. melitensis phenotypes were previously uncharacterized.

Purpose of the Study:

  • Investigate the effect of aiiD gene overexpression on B. melitensis.
  • Characterize the exopolysaccharide (EPS) involved in clumping.
  • Assess the role of QS-deficient B. melitensis in biofilm formation and host cell adhesion.

Main Methods:

  • Overexpression of the aiiD gene in B. melitensis.
  • Analysis of bacterial clumps for exopolysaccharide and DNA content.
  • Characterization of outer membrane vesicle production.
  • Purification and structural analysis of the exopolysaccharide.
  • Biofilm attachment assays and HeLa cell infection models.

Main Results:

  • aiiD overexpression induced bacterial clumping and increased outer membrane vesicle production.
  • Exopolysaccharide and DNA were identified as major components of the bacterial clumps.
  • The B. melitensis 16M exopolysaccharide has a molecular weight of ~16 kDa, composed of glucosamine, glucose, and mannose, with specific mannosyl linkages.
  • The clumping strain exhibited enhanced adhesion to polystyrene and HeLa cells.

Conclusions:

  • The aiiD gene product, AiiD, degrades AHLs, leading to a QS-deficient and clumping B. melitensis strain.
  • The characterized exopolysaccharide contributes to increased bacterial adherence and biofilm formation.
  • These findings support the hypothesis that Brucella melitensis can form biofilms during its lifecycle.

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