TABLE 2.

Siderophore production by C. diphtheriae strains

Supplement in PGTH mediumbSiderophore unitsa
1737 (wt)1737A1737E1737E/pKEC7 (wt)C7AC7EC7E/pKEPW8
+Fe2.63.72.57.710.110.710.811.19.4
−Fe23.622.94.845.256.245.715.771.219.5
  • a Siderophore units were determined as described previously (33). Values are the means of three independent experiments, and the results of each experiment varied by less than 15% from the mean.

  • b +Fe contained 5 μM FeSO4; −Fe contained no added supplement.