FIG. 10.

Upstream Crp binding site is essential for pla expression: schematic representation of the pla gene and different Ppla-lacZ transcriptional fusions (not to scale). The pla promoter region is indicated by a thin black line with two black boxes representing the half-sites of the Crp binding site. The pla open reading frame is indicated by a thick black line, and the lacZ open reading frame is indicated by a thick gray line. Each fusion, located on a plasmid (Table 1), was transformed into Y. pestis, and the level of β-galactosidase (β-gal.) expression was determined for samples collected following cultivation in buffered L medium. Each assay was completed at least three times, and the means ± standard deviations are shown.