The heterologous siderophores ferrioxamine B and ferrichrome activate signaling pathways in Pseudomonas aeruginosa.
Pseudomonas aeruginosa secretes two siderophores, pyoverdine and pyochelin, under iron-limiting conditions. These siderophores are recognized at the cell surface by specific outer membrane receptors, also known as TonB-dependent receptors. In addition, this bacterium is also able to incorporate many heterologous siderophores of bacterial or fungal origin, which is reflected by the presence of 32 additional genes encoding putative TonB-dependent receptors. In this work, we have used a proteomic approach to identify the inducing conditions for P. aeruginosa TonB-dependent receptors. In total, 11 of these receptors could be discerned under various conditions. Two of them are only produced in the presence of the hydroxamate siderophores ferrioxamine B and ferrichrome. Regulation of their synthesis is affected by both iron and the presence of a cognate siderophore. Analysis of the P. aeruginosa genome showed that both receptor genes are located next to a regulatory locus encoding an extracytoplasmic function sigma factor and a transmembrane sensor. The involvement of this putative regulatory locus in the specific induction of the ferrioxamine B and ferrichrome receptors has been demonstrated. These results show that P. aeruginosa has evolved multiple specific regulatory systems to allow the regulation of TonB-dependent receptors.
VU Medical Center, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands. m.llamas@vumc.nl
María A
MA
Llamas
Marion
M
Sparrius
Roy
R
Kloet
Connie R
CR
Jiménez
Christina
C
Vandenbroucke-Grauls
Wilbert
W
Bitter
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport / Q000502:physiology; D003676:Deferoxamine / Q000378:metabolism*; D005290:Ferric Compounds / Q000378:metabolism*; D005291:Ferrichrome / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017262:Siderophores / Q000378:metabolism*; D015398:Signal Transduction
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D005290:Ferric Compounds; C489524:FoxA protein, bacteria; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D017262:Siderophores; C057616:tonB protein, Bacteria; D005291:Ferrichrome; C002577:ferrioxamine B; D003676:Deferoxamine