Effect of nisin induction on ebpR and ebpA expression. Cells were grown to an OD600 nm of ~0.8 (3 hr, late log exponential growth phase) and at this point cells were left untreated (0) or treated with increasing concentration of nisin (from 0.005 to 10 ng/ml). Then, cells were collected and RNA extracted. After reverse transcription, ebpA and ebpR cDNA was quantified by real time PCR. The strains were OG1RF or ΔebpR (TX5514) carrying either the empty plasmid (-) or ebpR in trans under the nisin promoter (+). ebpR (gray bars) and ebpA (white bars) transcript levels were normalized with gyrB transcript levels. The data correspond to the mean of two independent experiments.