title: Role of FlbT in flagellin production in Brucella melitensis.
abstract: It was recently demonstrated that the pathogen Brucella melitensis produces a polar sheathed flagellum under the control of the master regulator FtcR. However, the regulatory mechanism controlling the flagellar assembly remains unknown. In this work, we investigate the flagellar hierarchy of B. melitensis as well as the flagellin FliC regulation. We show that a mutation in fliF or flgE (coding for the basal body structure and the hook, respectively) does not affect FliC synthesis, suggesting that production of FliC does not depend on the flagellar assembly. We demonstrate that FlbT is a FliC activator since inactivation of flbT causes a decrease in fliC expression by using a fliC-lacZ translational reporter construct. Moreover, the quantitative real-time PCR and Western blot analysis show a marked decrease in fliC mRNA and FliC protein level, respectively. Conversely, the B. melitensis wild-type strain overexpressing flaF fails to produce FliC, suggesting an opposite function. Interestingly, the expression of the flbT gene in an ftcR or an flbT mutant restores FliC production, demonstrating that FlbT plays a regulatory checkpoint role in FliC synthesis. This mechanism could be conserved in the Rhizobiales since complementation of an flbT or an ftcR mutant with flbT from Sinorhizobium meliloti restores FliC synthesis.
authors.affiliation: Unité de Recherche en Biologie Moléculaire (URBM), Facultés Universitaires Notre-Dame de la Paix Namur (FUNDP), 61 rue de Bruxelles, B-5000 Namur, Belgium.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Ferooz
authors.affiliation: Unité de Recherche en Biologie Moléculaire (URBM), Facultés Universitaires Notre-Dame de la Paix Namur (FUNDP), 61 rue de Bruxelles, B-5000 Namur, Belgium.
authors.forename: Julien
authors.initials: J
authors.lastname: Lemaire
authors.affiliation: Unité de Recherche en Biologie Moléculaire (URBM), Facultés Universitaires Notre-Dame de la Paix Namur (FUNDP), 61 rue de Bruxelles, B-5000 Namur, Belgium.
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Letesson
mesh_terms: D017347:Brucella melitensis / Q000235:genetics / Q000378:metabolism*; D005407:Flagella / Q000235:genetics / Q000378:metabolism; D005408:Flagellin / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial
chemical_list: D005408:Flagellin