Figure 2. LVS ΔfeoB′ is defective for ferrous uptake but is capable of siderophore production and utilization.

A and B, ⁵⁵Fe ferrous iron uptake. LVS and ΔfeoB′ strains were grown overnight to mid-logarithmic phase in iron-limiting liquid che-CDM and rates of ferrous iron uptake were determined at 0.1 and 3 μM [⁵⁵Fe²⁺] in the presence of ascorbate. C, Siderophore production. Culture supernatants of LVS, ΔfslA, ΔfeoB′ strains grown overnight under iron-limitation were tested in the CAS assay and siderophore activity was normalized to OD₆₀₀. D, Siderophore-mediated ⁵⁵Fe uptake. ⁵⁵Fe-bound siderophore was incubated with bacteria grown in iron-limiting che-CDM and the rate of ⁵⁵Fe uptake was determined. Values were expressed as the means ± S.D. Significance was calculated relative to LVS values. ***p<0.001.