are sensitive to induction of carbamoyl phosphate synthetase. Cells were grown at 37°C in nutrient broth with (A) no additions or (B) supplemented with 0.1 mM IPTG. Growth was monitored by optical density at 650 nm. All strains contain an insertion in argI, the gene encoding ornithine carbamoyltransferase, and harbor plasmid-encoded CarB under the control of an IPTG-inducible promoter. Strains are represented in the figure legends by the Rid protein they lack. Strain names and relevant genotypes are RidA (DM14200), Rid2 (DM14307), Rid7 (DM14223), and control (DM14203). Data shown are representative of at least three independent experiments done in biological triplicate on separate days.