FIG. 4.

Xenosiderophore-stimulated growth of FA19 and isogenic mtr and mtr tonB mutant strains. Strains were grown in CDM containing 2.5 μM bovine transferrin, supplemented with 10 μM ferric citrate (positive control), 7.5 μM human transferrin, 10 μM enterobactin, or 10 μM salmochelin S2. Each time point represents the mean and standard deviation of results from three independent experiments. The strains used in this study were FA19 (wild type [WT]), KH12 (mtrC), KH14 (mtrD), MCV920 (mtrC tonB), and MCV921 (mtrD tonB).