FIG 10.

Siderophore production and uptake are necessary for bacterial movement in planta. DC283, ΔiucA, ΔiutA, ΔiucA/iucA⁺, and ΔiutA/iutA⁺ strains constitutively expressing GFP from plasmid pHC60 were used to inoculate sweet corn seedlings (cv. Jubilee) in a partial incision on the leaf surface. Plants were inoculated with 2 μl of bacterial suspension containing ∼10⁷ cells in 1× PBS-T. After 72 h, the distance of movement was quantified by measuring the length of GFP fluorescence in the basipetal direction using a Leica MZ FLIII fluorescence equipped stereoscope (Leica Microsystems). Fluorescent microsphere beads (FluoSpheres) were used as a negative control to correct for passive movement. The results are expressed as the mean distance from the inoculation point for at least 10 replicates for each strain ± the standard errors of the mean.