Fig 3.

Utilization of a ferric-pyoverdine complex by a siderophore-deficient mutant of Pf-5. Five microliters of an 8 μM solution of pyoverdine B10-2 (from Pseudomonas sp. strain B10) was spotted in the center of each plate containing an iron-limited medium (KMB amended with 600 mM 2,2′-dipyridyl). Ten microliters of a cell suspension (∼10⁶ CFU/ml) of a pvdI-pchA mutant of Pf-5 (Fpv⁺) or the pvdI-pchA mutant with a deletion in one of six fpv genes (fpvU, fpvV, fpvX, fpvY, or fpvZ) was spotted 1 cm from the center of the plate. The plate was incubated at 27°C for 2 days. Growth of all strains with the exception of the pvdI-pchA-fpvW mutant was observed, indicating that FpvW is required for uptake of pyoverdine B10-2.