title: EmbRS a new two-component system that inhibits biofilm formation and saves Rubrivivax gelatinosus from sinking.
abstract: Photosynthetic bacteria can switch from planktonic lifestyle to phototrophic biofilm in mats in response to environmental changes. The mechanisms of phototrophic biofilm formation are, however, not characterized. Herein, we report a two-component system EmbRS that controls the biofilm formation in a photosynthetic member of the Burkholderiales order, the purple bacterium Rubrivivax gelatinosus. EmbRS inactivation results in cells that form conspicuous bacterial veils and fast-sinking aggregates in liquid. Biofilm analyses indicated that EmbRS represses the production of an extracellular matrix and biofilm formation. Mapping of transposon mutants that partially or completely restore the wild-type (WT) phenotype allowed the identification of two gene clusters involved in polysaccharide synthesis, one fully conserved only in Thauera sp., a floc-forming wastewater bacterium. A second two-component system BmfRS and a putative diguanylate cyclase BdcA were also identified in this screen suggesting their involvement in biofilm formation in this bacterium. The role of polysaccharides in sinking of microorganisms and organic matter, as well as the importance and the evolution of such regulatory system in phototrophic microorganisms are discussed.
authors.affiliation: CNRS, CGM, UPR 3404, Université Paris Sud, 1 Ave. de la Terrasse, Gif-sur-Yvette, F-91198, France.
authors.forename: Anne Soisig
authors.initials: AS
authors.lastname: Steunou
authors.forename: Sylviane
authors.initials: S
authors.lastname: Liotenberg
authors.forename: Marie-Noêlle
authors.initials: MN
authors.lastname: Soler
authors.forename: Romain
authors.initials: R
authors.lastname: Briandet
authors.forename: Valérie
authors.initials: V
authors.lastname: Barbe
authors.forename: Chantal
authors.initials: C
authors.lastname: Astier
authors.forename: Soufian
authors.initials: S
authors.lastname: Ouchane
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D020562:Betaproteobacteria / Q000235:genetics / Q000502:physiology*; D018441:Biofilms / Q000254:growth & development*; D004251:DNA Transposable Elements; D015964:Gene Expression Regulation, Bacterial; D016254:Mutagenesis, Insertional; D011135:Polysaccharides, Bacterial / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D011135:Polysaccharides, Bacterial; D014157:Transcription Factors