FIG. 1.

Amounts of NifA and NifL in wild-type and fnr mutant strains of E. coli. Cultures were grown at 30^°C in minimal medium under anaerobic conditions with 4 mM glutamine as a limiting nitrogen source. The strains carried K. pneumoniae NifL and NifA under the control of the tac promoter on pNH3. Expression of NifL and NifA was induced with 10 μM IPTG in the wild-type strain (lanes 2 and 8), in fnr null allele strains RAS7 (lanes 3 and 9) and RAS14 (lanes 5 and 11), and in complemented strains RAS10 (lanes 4 and 10) and RAS16 (lanes 6 and 12). The amounts of NifL (A) and NifA (B) were determined by Western blotting. Prestained broad-range protein markers (lanes 1 and 7) were purchased from New England Biolabs.