FIG. 1.

Effect of drugs on growth of E. coli cells expressing or not expressing the NorMI protein of B. melitensis. E. coli AG100A harboring a vector expressing NorMI from B. melitensis (pUC19-NorMI) (▴) or harboring the vector alone (pUC19) (○) was grown for 20 h at 37°C (with agitation) in Mueller-Hinton medium containing twofold-increasing concentrations of norfloxacin (1.5625 to 200 ng/ml), ciprofloxacin (0.3125 to 40 ng/ml), gentamicin (31.25 to 4,000 ng/ml), tetraphenylphosphonium bromide (1 to 128 μg/ml), acriflavine (0.25 to 32 μg/ml), or berberine (3.125 to 400 μg/ml). Bacterial growth was monitored by turbidimetry (at 600 nm). The growth index, calculated by dividing the OD₆₀₀ of the culture in the presence of drug by the OD₆₀₀ of the culture in the absence of drug, is shown.