Figure 3. Transcriptional fusion analysis of the cAMP–CRP regulation of tfoX expression.

(A) The β-galactosidase expression in V. cholerae strains C7258∆lacZ (WT) and WL7258∆lacZ (∆crp) containing a ptfoX^VC–lacZ transcriptional fusion. (B) The luminescence activity in V. fluvialis strains 85003 (WT) and 85003∆crp (∆crp) containing a ptfoX^VF–lux transcriptional fusion. All strains were grown at 37 °C with shaking to the mid-log phase. The β-Galactosidase and bioluminescence activity were measured as described in the Methods. Error bars indicate the standard deviations of three independent cultures. ***Significantly different from the wild-type strain (t-test, P < 0.005).