Fig. 3.

Growth of Y. pestis KIM strains in deferrated PMH2 at 37°C. A Δpsn mutant produces and secretes Ybt but cannot use the siderophore to obtain iron. A Δirp2 mutant cannot make the Ybt siderophore. The Δpsn Δirp2 mutant is defective in both biosynthesis and uptake. Y. pestis cells were acclimated to growth under iron-deficient conditions as previously described by Fetherston et al [42] which shows a similar experiment.