Fig. 4
β-Lactamase activity of E. coli after transformation with various retroviral plasmids. Heat-shock competent E. coli Stbl3 cells were transformed with either no plasmid DNA (mock) or one of the following retroviral plasmids: pBabe Puro, pBMN-I-EGFP/Puro, pBMN-I-EGFP-2A-Puro, prBMN-I-EGFP-2A-Puro, pBMN-I-GFP, or prBMN-I-EGFP. The transformed cells were inoculated into LB medium containing 50 µg/mL carbenicillin and grown at 37 °C to stationary phase. Discs impregnated with the chromogenic cephalosporin nitrocefin were moistened with purified water, and bacterial suspensions were applied to the disc surface to observe for color changes. The results shown are representative of two independent experiments.
