Figure 4.

Reversion is reduced by inhibiting growth of cells with a lac amplification. (A) Tester strains were FC40 (no Tn10), TT23242 (Tn10 in the chromosome), TT22951 (Tn10 in the plasmid mhpC gene 4.6 kb from lac). Strain TT23241 served as scavenger. “+Tc” and “−Tc” indicate presence or absence of Tc (10 μg/ml) in selection plates. (B) Tester strains were FC40 (no Tn10), TT23242 (Tn10 in chromosome), TT22951 (Tn10 4.6 kb from lac). Strains TT23243, TT23244, and TT23245 carried Tn10 >30 kb, >30 kb, and 20 kb from lac, respectively. Without chlortetracycline (CTc), all strains showed reversion like FC40.