FIG. 2.
Site-directed mutagenesis of the araABDLMNPQ-abfA operon promoter. (A) The DNA sequence of the promoter is represented from position −12 to position +57, relative to the transcriptional start site of the araA gene. The −10 region is underlined and the AraR operators ORA1 and ORA2 are in shaded boxes. The single nucleotide changes introduced in ORA1 or ORA2 are shown. The sequence of the different DNA fragments and the position of its insertion between ORA1 and ORA2 are indicated. (B) Plasmids containing different araA-lacZ promoter fusions were integrated at the amyE locus of the B. subtilis 168T+ wild-type chromosome as described (see Materials and Methods). The strains containing the various mutated araA promoters were grown on C minimal medium supplemented with 1% (wt/vol) casein hydrolysate in the absence or presence of 0.4% (wt/vol) l-arabinose. The levels of accumulated β-galactosidase activity were measured 2 h after induction. AraR repression was calculated as the ratio between the level of expression (Miller units) obtained in the presence of l-arabinose and the value determined in absence of inducer.