title: Brucella melitensis 16M produces a mannan and other extracellular matrix components typical of a biofilm.
abstract: Mutations in the Brucella melitensis quorum-sensing (QS) system are involved in the formation of clumps containing an exopolysaccharide. Here, we show that the overexpression of a gene called aiiD in B. melitensis gives rise to a similar clumping phenotype. The AiiD enzyme degrades AHL molecules and leads therefore to a QS-deficient strain. We demonstrated the presence of exopolysaccharide and DNA, two classical components of extracellular matrices, in clumps produced by this strain. We also observed that the production of outer membrane vesicles is strongly increased in the aiiD-overexpressing strain. Moreover, this strain allowed us to purify the exopolysaccharide and to obtain its composition and the first structural information on the complex exopolysaccharide produced by B. melitensis 16M, which was found to have a molecular weight of about 16 kDa and to be composed of glucosamine, glucose and mostly mannose. In addition, we found the presence of 2- and/or 6-substituted mannosyl residues, which provide the first insights into the linkages involved in this polymer. We used a classical biofilm attachment assay and an HeLa cell infection model to demonstrate that the clumping strain is more adherent to polystyrene plates and to HeLa cell surfaces than the wild-type one. Taken together, these data reinforce the evidence that B. melitensis could form biofilms in its lifecycle.
authors.affiliation: Unité de Recherche en Biologie Moléculaire, Facultés Universitaires Notre-Dame de la Paix, Namur, Belgium.
authors.forename: Marie
authors.initials: M
authors.lastname: Godefroid
authors.forename: Mona V
authors.initials: MV
authors.lastname: Svensson
authors.forename: Pierre
authors.initials: P
authors.lastname: Cambier
authors.forename: Sophie
authors.initials: S
authors.lastname: Uzureau
authors.forename: Aurélie
authors.initials: A
authors.lastname: Mirabella
authors.forename: Xavier
authors.initials: X
authors.lastname: De Bolle
authors.forename: Pierre
authors.initials: P
authors.lastname: Van Cutsem
authors.forename: Göran
authors.initials: G
authors.lastname: Widmalm
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Letesson
mesh_terms: D001422:Bacterial Adhesion; D018441:Biofilms / Q000254:growth & development*; D001704:Biopolymers / Q000378:metabolism*; D017347:Brucella melitensis / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D004783:Environmental Microbiology; D017353:Gene Deletion; D015870:Gene Expression; D006367:HeLa Cells / Q000382:microbiology; D006801:Humans; D008351:Mannans / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D008970:Molecular Weight; D011137:Polystyrenes; D053038:Quorum Sensing; D022142:Secretory Vesicles / Q000378:metabolism
chemical_list: D001704:Biopolymers; D008351:Mannans; D011137:Polystyrenes