Figure 1.

Mechanistic aspects of siderophore switching in P. aeruginosa facing iron limitation. (a) In the wild-type strain PAO1 (black circles) pyochelin synthesis was strongly reduced relative to the situation in PAO1ΔpvdD (open circles). This suggests pyoverdine-mediated suppression of pyochelin production in PAO1. By contrast, pyochelin had no effect on pyoverdine production: pyoverdine production did not differ between PAO1 and PAO1ΔpchEF (grey circles). (b) In the wild-type strain PAO1, pyoverdine production (black circles) is strongly downregulated in response to increasing iron supplementation, whereas pyochelin production (open circles) remains relatively high until approximately 10 μM FeCl₃. The differences in repression sensitivities result in a range of iron availabilities where pyochelin becomes the predominant siderophore. The production of each siderophore is represented as RFU_siderophore/OD, relative to the standard medium without iron supplementation.