Present address: AgResearch Wallaceville, Ward Street, Upper Hutt, New Zealand.
Siderophore-mediated cell signalling in Pseudomonas aeruginosa: divergent pathways regulate virulence factor production and siderophore receptor synthesis
Article first published online: 18 DEC 2002
Volume 47, Issue 1, pages 195–207, January 2003
How to Cite
Beare, P. A., For, R. J., Martin, L. W. and Lamont, I. L. (2003), Siderophore-mediated cell signalling in Pseudomonas aeruginosa: divergent pathways regulate virulence factor production and siderophore receptor synthesis. Molecular Microbiology, 47: 195–207. doi: 10.1046/j.1365-2958.2003.03288.x
- Issue published online: 18 DEC 2002
- Article first published online: 18 DEC 2002
- Accepted 23 September, 2002.
Under iron-limiting conditions, Pseudomonas aeruginosa produces a siderophore called pyoverdine. Pyoverdine is secreted into the extracellular environment where it chelates iron, and the resulting ferri-pyoverdine complexes are transported back into the bacteria by a cell surface receptor protein FpvA. Pyoverdine also acts as a signalling molecule inducing the production of three secreted virulence factors. Binding of ferri-pyoverdine to FpvA transduces a signal to the periplasmic part of the membrane-spanning antisigma factor FpvR. The signal is transmitted to the cytoplasmic part of FpvR, which controls the activity of an extracytoplasmic family (ECF) sigma factor protein PvdS. This results in the production of the virulence factors pyoverdine, exotoxin A and PrpL endoprotease. Here, we show that a second divergent branch of this signalling pathway regulates the production of the FpvA protein. FpvR negatively regulates the activity of a second ECF sigma factor, FpvI, which is required for the synthesis of FpvA, and the presence of ferri-pyoverdine greatly increases the activity of FpvI so that production of FpvA is induced. To the best of our knowledge, this is the first example of a branched signalling system of this sort and the first example of an antisigma factor protein (FpvR) that directly regulates the activities of two different ECF sigma factor proteins (PvdS and FpvI).