FIG. 5.

Effect of the simultaneous inactivation of the crc and cyo genes on catabolic repression of the PalkB promoter. P. putida strains PBS4, PBS4B1 (PBS4 with a knockout mutation at the cyoB gene), PBS4C1 (PBS4 with a knockout mutation at the crc gene), and PBS4BC1 (PBS4 with knockout mutations at the cyoB and crc genes) were grown in duplicate flasks in LB medium. At an A₆₀₀ of 0.08, the nonmetabolizable inducer DCPK was added to one of the flasks, whereas the other flask was left as a noninduced control. Aliquots were taken at different times, and the β-galactosidase activity was measured. The levels of β-galactosidase are represented as a function of cell growth. The plot shows the values observed for induced cultures (noninduced cultures had very low β-galactosidase activities [30 to 90 Miller units] and are not represented). The values shown correspond to several independent assays, all represented on the same plot.