Figure 4. E. coli cirA expression is upregulated in response to iron limitation.

(A) An overnight culture of Ec^MG1655 carrying the reporter plasmid p^{cirA -luc} was re-inoculated 1∶20 in fresh LB with indicated supplements (0.25 µg/ml mitomycin C; 100 mM DTPA) and grown under aeration for 4 h. OD₆₀₀ of the cultures was normalized, bacteria were harvested and luciferase-activity was measured in bacterial lysates. Relative luminescence units (RLU) per unit OD₆₀₀ are indicated. (B) Overnight cultures of Ec^MG1655 as well as Ec^{MG1655 ΔcirA} were re-inoculated 1∶20 in fresh LB with indicated supplements (0.25 µg/ml mitomycin C; 100 mM DTPA) and grown under aeration for 4 h. Cultures were normalized to OD₆₀₀, bacteria were harvested and CirA was detected in bacterial lysates by immunoblot using a rabbit-α-CirA antiserum. E. coli cytoplasmic protein DnaK was detected as loading control.