FIG. 3.

β-Galactosidase activity measurements of wild-type and mutant promoter expression. (A) Activity of the regB reporter plasmid pRegB01 (left) and the wild-type senC reporter plasmid pReg-operon (right) in wild-type (SB1003), regB mutant (SD01), and regA-disrupted (MS01) cells. A plus or minus sign indicates growth in the presence or absence of oxygen. (B) Activities of promoter mutant vectors pReg-M52 (left) and pRegM08 (right) harbored in the same strains as in panel A. Units of activity are micromoles of ONPG (o-nitrophenyl-β-d-galactopyranoside) hydrolyzed per minute per milligram of protein. The results shown are averages of at least three independent assays.