FIG. 5.

Effect of the addition of cAMP on the expression of β-galactosidase from strains CCB21 and CCB21H. Cells were grown in LB medium with 0.5 M NaCl and in LB medium without NaCl. When the cultures reached an OD₆₀₀ of 0.5, samples were taken for β-galactosidase measurements (time zero), and cAMP was immediately added to the cultures. Additional samples were then taken for β-galactosidase measurements at the indicated times. Each bar represents the relative activity determined as the ratio of the β-galactosidase activities (Miller units) of the hha (CCB21H) and hha⁺ (CCB21) strains.