title: Roles of type IV pili, flagellum-mediated motility and extracellular DNA in the formation of mature multicellular structures in Pseudomonas aeruginosa biofilms.
abstract: When grown as a biofilm in laboratory flow chambers Pseudomonas aeruginosa can develop mushroom-shaped multicellular structures consisting of distinct subpopulations in the cap and stalk portions. We have previously presented evidence that formation of the cap portion of the mushroom-shaped structures in P. aeruginosa biofilms occurs via bacterial migration and depends on type IV pili (Mol Microbiol 50: 61-68). In the present study we examine additional factors involved in the formation of this multicellular substructure. While pilA mutants, lacking type IV pili, are deficient in mushroom cap formation, pilH and chpA mutants, which are inactivated in the type IV pili-linked chemosensory system, showed only minor defects in cap formation. On the contrary, fliM mutants, which are non-flagellated, and cheY mutants, which are inactivated in the flagellum-linked chemotaxis system, were largely deficient in cap formation. Experiments involving DNase treatment of developing biofilms provided evidence that extracellular DNA plays a role in cap formation. Moreover, mutants that are deficient in quorum sensing-controlled DNA release formed microcolonies upon which wild-type bacteria could not form caps. These results constitute evidence that type IV pili, flagellum-mediated motility and quorum sensing-controlled DNA release are involved in the formation of mature multicellular structures in P. aeruginosa biofilms.
authors.affiliation: Centre for Biomedical Microbiology, Technical University of Denmark, DK-2800, Lyngby, Denmark.
authors.forename: Kim B
authors.initials: KB
authors.lastname: Barken
authors.forename: Sünje J
authors.initials: SJ
authors.lastname: Pamp
authors.forename: Liang
authors.initials: L
authors.lastname: Yang
authors.forename: Morten
authors.initials: M
authors.lastname: Gjermansen
authors.forename: Jacob J
authors.initials: JJ
authors.lastname: Bertrand
authors.forename: Mikkel
authors.initials: M
authors.lastname: Klausen
authors.forename: Michael
authors.initials: M
authors.lastname: Givskov
authors.forename: Cynthia B
authors.initials: CB
authors.lastname: Whitchurch
authors.forename: Joanne N
authors.initials: JN
authors.lastname: Engel
authors.forename: Tim
authors.initials: T
authors.lastname: Tolker-Nielsen
mesh_terms: D001422:Bacterial Adhesion; D018441:Biofilms / Q000254:growth & development*; D002633:Chemotaxis; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D005109:Extracellular Matrix / Q000235:genetics / Q000382:microbiology; D036781:Fimbriae Proteins / Q000235:genetics; D010861:Fimbriae, Bacterial / Q000235:genetics*; D005407:Flagella / Q000235:genetics*; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D005838:Genotype; D018613:Microscopy, Confocal; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D053038:Quorum Sensing
chemical_list: D004269:DNA, Bacterial; C086589:pilH protein, Pseudomonas aeruginosa; D036781:Fimbriae Proteins