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Journal of Bacteriology, June 2009, p. 3517-3525, Vol. 191, No. 11
0021-9193/09/$08.00+0     doi:10.1128/JB.00010-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

The Pseudomonas aeruginosa Pyochelin-Iron Uptake Pathway and Its Metal Specificity{triangledown}

Armelle Braud, Mélissa Hannauer, Gaëtan L. A. Mislin, and Isabelle J. Schalk*

Métaux et Microorganismes: Chimie, Biologie et Applications, FRE3211-LC1, CNRS-Université de Strasbourg, ESBS, Blvd Sébastien Brant, F-67413 Illkirch, Strasbourg, France

Received 5 January 2009/ Accepted 13 March 2009

Pyochelin (Pch) is one of the two major siderophores produced and secreted by Pseudomonas aeruginosa PAO1 to assimilate iron. It chelates iron in the extracellular medium and transports it into the cell via a specific outer membrane transporter, FptA. We used the fluorescent properties of Pch to show that this siderophore chelates, in addition to Fe3+ albeit with substantially lower affinities, Ag+, Al3+, Cd2+, Co2+, Cr2+, Cu2+, Eu3+, Ga3+, Hg2+, Mn2+, Ni2+, Pb2+, Sn2+, Tb3+, Tl+, and Zn2+. Surprisingly, the Pch complexes with all these metals bound to FptA with affinities in the range of 10 nM to 4.8 µM (the affinity of Pch-Fe is 10 nM) and were able to inhibit, with various efficiencies, Pch-55Fe uptake in vivo. We used inductively coupled plasma atomic emission spectrometry to follow metal uptake by P. aeruginosa. Energy-dependent metal uptake, in the presence of Pch, was efficient only for Fe3+. Co2+, Ga3+, and Ni2+ were also transported, but the uptake rates were 23- to 35-fold lower than that for Fe3+. No uptake was seen for all the other metals. Thus, cell surface FptA has broad metal specificity at the binding stage but is much more selective for the metal uptake process. This uptake pathway does not appear to efficiently assimilate any metal other than Fe3+.

* Corresponding author. Mailing address: Métaux et Microorganismes: Chimie, Biologie et Applications, FRE 3211, ESBS, Blvd Sébastien Brant, BP 10412, F-67413 Illkirch, Strasbourg, France. Phone: 33 3 90 24 47 19. Fax: 33 3 90 24 48 29. E-mail: schalk{at}esbs.u-strasbg.fr

{triangledown} Published ahead of print on 27 March 2009.

Journal of Bacteriology, June 2009, p. 3517-3525, Vol. 191, No. 11
0021-9193/09/$08.00+0     doi:10.1128/JB.00010-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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