By using a lacZ operon fusion genomic library of the Escherichia coli O157:H7 Sakai, we identified phosphate-starvation-inducible (psi) promoters located upstream of the yibD and ytfK genes. They have been previously proposed to belong to the phosphate regulon (pho regulon) by Beak and Lee (2006), based on the DNA array and in vivo transcriptional experiments. However, the direct interaction of these promoters with the activator protein of the pho regulon, PhoB, has not been determined. We determined the binding regions of PhoB in these promoter regions by DNase I footprinting. Both regions contained two pho boxes similar to the consensus sequence for PhoB binding.