FIG. 5.

β-Galactosidase activities in E. coli DH5α driven by the rpoS-lacZ (pRPO220B) and psrA-lacZ (pPPSRA220) fusions. Plasmid pQEPSRA contains the psrA gene and expresses the PsrA protein, whereas plasmid pQE30 is the vector (see text for details). All measurements were done in triplicate; the mean and standard error are shown. Cells harboring plasmids were grown for 16 h in LB medium in the presence of appropriate antibiotics. Columns: A, E. coli(pQE30)(pPPSR220); B, E. coli(pQEPSRA)(pPPSR220); C, E. coli(pQE30)(pRPO220B); D, E. coli(pQEPSRA)(pRPO220B).