title: Real time fluorescent resonance energy transfer visualization of ferric pyoverdine uptake in Pseudomonas aeruginosa. A role for ferrous iron.
abstract: To acquire iron, Pseudomonas aeruginosa secretes a major fluorescent siderophore, pyoverdine (PvdI), that chelates iron and shuttles it into the cells via the specific outer membrane transporter, FpvAI. We took advantage of the fluorescence properties of PvdI and its metal chelates as well as the efficient FRET between donor tryptophans in FpvAI and PvdI to follow the fate of the siderophore during iron uptake. Our findings with PvdI-Ga and PvdI-Cr uptake indicate that iron reduction is required for the dissociation of PvdI-Fe, that a ligand exchange for iron occurs, and that this dissociation occurs in the periplasm. We also observed a delay between PvdI-Fe dissociation and the rebinding of PvdI to FpvAI, underlining the kinetic independence of metal release and siderophore recycling. Meanwhile, PvdI is not modified but recycled to the medium, still competent for iron chelation and transport. Finally, in vivo fluorescence microscopy revealed patches of PvdI, suggesting that uptake occurs via macromolecular assemblies on the cell surface.
authors.affiliation: Métaux et Microorganismes: Chimie, Biologie, et Applications, UMR 7175-LC1 Institut Gilbert-Laustriat, CNRS-Université Louis Pasteur, ESBS, Boulevard Sébastien Brant, F-67413 Illkirch, Strasbourg, France.
authors.forename: Jason
authors.initials: J
authors.lastname: Greenwald
authors.forename: Françoise
authors.initials: F
authors.lastname: Hoegy
authors.forename: Mirella
authors.initials: M
authors.lastname: Nader
authors.forename: Laure
authors.initials: L
authors.lastname: Journet
authors.forename: Gaëtan L A
authors.initials: GL
authors.lastname: Mislin
authors.forename: Peter L
authors.initials: PL
authors.lastname: Graumann
authors.forename: Isabelle J
authors.initials: IJ
authors.lastname: Schalk
mesh_terms: D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D005296:Ferrous Compounds / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000378:metabolism; D007700:Kinetics; D008856:Microscopy, Fluorescence; D009842:Oligopeptides / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000254:growth & development / Q000378:metabolism*
chemical_list: D005296:Ferrous Compounds; D007502:Iron Chelating Agents; D009842:Oligopeptides; C042453:pyoverdin; D007501:Iron