TABLE 2.

Activation of the K. pneumoniae nifH promoter by the H. seropedicae N-terminally truncated NifA protein in E. coli^a

Plasmids in ET8894	Activator	β-Galactosidase activity (Miller units)
		−N/−O	−N/+O	+N/−O
pRT22/pNH11	NifA (K. pneumoniae)	19,582	20,904	20,800
pRT22/pEMS130	NifA (H. seropedicae)	21	15	19
pRT22/pEMS131	ΔR NifA (H. seropedicae)	2,884	31	3,016

^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) and IPTG with the following additions: N-free minimal medium under nitrogen (−N/−O), N-free minimal medium under air (−N/+O), and minimal medium plus NH₄Cl (20 mM) under nitrogen (+N/−O). β-Galactosidase activities were measured after 20 to 24 h of incubation at 30°C.