title: Effects of iron on DNA release and biofilm development by Pseudomonas aeruginosa.
abstract: Extracellular DNA is one of the major matrix components in Pseudomonas aeruginosa biofilms. It functions as an intercellular connector and plays a role in stabilization of the biofilms. Evidence that DNA release in P. aeruginosa PAO1 biofilms is controlled by the las-rhl and pqs quorum-sensing systems has been previously presented. This paper provides evidence that DNA release in P. aeruginosa PAO1 biofilms is also under iron regulation. Experiments involving cultivation of P. aeruginosa in microtitre trays suggested that pqs expression, DNA release and biofilm formation were favoured in media with low iron concentrations (5 microM FeCl(3)), and decreased with increasing iron concentrations. Experiments involving cultivation of P. aeruginosa in a flow-chamber system suggested that a high level of iron (100 microM FeCl(3)) in the medium suppressed DNA release, structural biofilm development, and the development of subpopulations with increased tolerance toward antimicrobial compounds. Experiments with P. aeruginosa strains harbouring fluorescent reporters suggested that expression of the pqs operon was induced in particular subpopulations of the biofilm cells under low-iron conditions (1 microM FeCl(3)), but repressed in the biofilm cells under high-iron conditions (100 microM FeCl(3)).
authors.affiliation: Centre for BioScience and Technology, BioCentrum-DTU, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Liang
authors.initials: L
authors.lastname: Yang
authors.affiliation: Centre for BioScience and Technology, BioCentrum-DTU, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Kim B
authors.initials: KB
authors.lastname: Barken
authors.affiliation: Centre for BioScience and Technology, BioCentrum-DTU, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Mette E
authors.initials: ME
authors.lastname: Skindersoe
authors.affiliation: Centre for BioScience and Technology, BioCentrum-DTU, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Allan B
authors.initials: AB
authors.lastname: Christensen
authors.affiliation: Centre for BioScience and Technology, BioCentrum-DTU, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Givskov
authors.affiliation: Centre for BioScience and Technology, BioCentrum-DTU, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Tim
authors.initials: T
authors.lastname: Tolker-Nielsen
mesh_terms: D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D004269:DNA, Bacterial / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects*; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics; D007501:Iron / Q000494:pharmacology*; D009876:Operon; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D053038:Quorum Sensing / Q000187:drug effects; D015398:Signal Transduction
chemical_list: D004269:DNA, Bacterial; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D007501:Iron