FIG. 3.

Plasmid-borne rluC complements the ΔrluC suppression. rluC was cloned into pBAD18 and introduced into KK33 (ΔbipA ΔrluC), and analysis of the growth rates at 20°C was performed. (A) When rluC expression was repressed by addition of glucose (glu), growth was similar whether cells contained the parental plasmid pBAD18 or the rluC-carrying plasmid pKK1. Some leaky expression in glucose was apparent, demonstrated by a slight decrease in the growth rate of pKK1-containing cells. Addition of arabinose (ara) to induce rluC expression had no effect on cells carrying the pBAD18 control, but the pKK1-containing bacteria suffered a decrease in growth rate. All strains were assayed in triplicate. (B) Expression of rluC(D144A), containing an active-site mutation (carried by pKK4), failed to complement the deletion of rluC, as growth was similar to that of cells growing in the presence of glucose or that of cells containing pBAD18. All strains were assayed in triplicate. The altered growth conditions for this experiment resulted in strains' entering stationary phase sooner than the strains in experiments without plasmids.