TABLE 3.

Growth stimulation of C. diphtheriae strains by iron and siderophore

StrainGrowth with various iron sources
Supa + 2.5 μM Fe3+Sup + 25 μM Fe3+Sup25 μM Fe3+50 μM Fe3+Aerobactinb
C7 (−) wt+c++++
C7E (ciuE)++++/−+
C7A (ciuA)+/−+/−+
C7p6A (irp6AΔ)++++/−+
C7A-1 (irp6A pt.)++++/−+
HC1++
1737 wt++++
1737A (ciuA)+/−+/−
1737E (ciuE)++++/−
  • a Sup, supernatant from C7 cultures grown for 24 h in low-iron PGTH medium.

  • b Aerobactin was from S. flexneri 2457T supernatant.

  • c ++, heavy growth; +, light growth; +/−, trace growth; −, no growth.