FIG. 7.

Chromosomal lacZ gene expression in quiescent cells. DS903hns-205 and DS903hns-205 containing the two-plasmid system for Rcd expression were grown initially in L broth at 30°C and then diluted in L broth prewarmed to 42°C containing 1 mM IPTG to induce expression of the lacZ gene. Carbenicillin (50 μg ml⁻¹) was added each hour to maintain selection for plasmid B8. DS903hns-205 containing the two-plasmid system reached an Rcd-induced quiescent state within 2 h, whereas the control culture continued to grow. β-Galactosidase activity is expressed in Miller units in the presence (black bars) and absence (white bars) of Rcd.