FIG. 3.

Plate assay for siderophore-mediated antibiosis. KB agar plates were inoculated in the center with 10 μl of a suspension (≅10⁶ CFU/ml) of the different Pseudomonas strains. The plates were incubated for 24 h at 28°C and then sprayed with a suspension of E. carotovora (≅10⁶ CFU/ml) and examined after additional 24-h incubation. The inhibition of E. carotovora is indicated by the transparent halo surrounding the Pseudomonas patch. The strain and medium are indicated below each plate. KB-Fe, KB medium; KB+Fe, KB supplemented with 100 μM FeCl₃.