TABLE 3.

Effect of iron and Desferal on the activity of the H. seropedicae N-terminally truncated and K. pneumoniae NifA proteins in E. coli^a

Addition	β-Galactosidase activity (Miller units)
	ET8894(pRT22/pNH11)	ET8894(pRT22/pEMS131)
1. −Fe	20,060	1,671
2. −Fe/+Desf	20,904	430
3. +Fe/+Desf	ND	1,612
4. +Fe	ND	2,750

^aE. coli ET8894 containing the indicated plasmids was grown in LB medium as described in Materials and Methods. Cells were inoculated in NFDM medium plus glutamine (10 μg/ml) with the following additions: 1, N-free minimal medium under nitrogen and no Fe added; 2, treatment 1 plus Desferal (250 μg/ml); 3, treatment 2 plus FeSO₄ · 7H₂O (20 μg/ml); 4, treatment 1 plus FeSO₄ · 7H₂O (20 μg/ml). β-Galactosidase activities were measured after 20 to 24 h of incubation at 30°C. ND, not determined.