RL211 antitermination assay
E. coli RL211 harbors the cat gene preceded by a Rho-independent trpL terminator and is sensitive to chloramphenicol (Cm). To test antitermination activity as described in Ammerman et al. (72), Bae et al. (73), and Landick et al. (74), the genes encoding StpA in the pET7C-HIS plasmid and PlzA, PlzA R145K and PlzA R145D in pET-45b(+) plasmid were electroporated into E. coliRL211 strain provided by Dr. Robert Landick (74). Transformed RL211 strains were grown in either with 100 µg/ml ampicillin or 50 µg/ml kanamycin overnight (OD600 0.9-1.0). Cultures were spotted (5 µl) on LB plates with and without 34 µg/ml Cm. Cells were grown for 1-3 d at 37°C. Plates were imaged in an Azure Sapphire imager.