FIG. 3.

Expression of nif1 genes in a nifB1 deletion mutant. (A) RT-PCR of genes of the nif1 cluster in the wild-type (wt) strain and in a nifB1 promoter deletion strain. The rnpB gene, which is constitutively expressed, was used as a control to show equal amounts of RNA (56). The percent expression was calculated from the intensity of the band in the nifB1 deletion strain compared to the wild-type strain, after normalizing each band first to rnpB. The two rnpB bands differed by <5%. The region of the gene that was amplified is denoted as a line over the corresponding gene next to the gel. (B) β-Galactosidase activity in a nifB1 deletion strain.