Fig. 4

Functional assays for pFCF1, pFCF2 and pFBH1. a CAS assays. Images are photographs of CAS agar plates spotted with various E. coli transformants. Enterobactin secretion is indicated by orange halos. Upper left panel: E. coli entA ⁻ strain transformed with pFCF1 (left spot) and pFCF1-entA (right spot). Lower left panel: E. coli entA ⁻ strain transformed with pFCF2 (left spot) and pFCF2- entA (right spot). Upper right panel: E. coli entE ⁻ strain transformed with pFCF1 (left spot) and pFCF1-entE (right spot). Lower right panel: E. coli entB ⁻ strain transformed with pFBH1 (left spot) and pFBH1-entB (right spot). b Growth studies of transformants in iron-depleted medium. Orange bars indicate strains/transformants that exhibited a positive CAS signal; error bars represent standard deviations from mean values (n = 3). Left to right: E. coli entA ⁻ strain transformed with pFCF1; E. coli entA ⁻ strain transformed with pFCF1-entA; E. coli entE ⁻ strain transformed with pFCF1; E. coli entE ⁻ strain transformed with pFCF1-entE; E. coli entB ⁻ strain transformed with pFBH1; E. coli entB ⁻ strain transformed with pFBH1-entB; E. coli entA ⁻ strain transformed with pFCF2; E. coli entA ⁻ strain transformed with pFCF2-entA