FIG 3.
Growth kinetics and metabolic activity of different strains under antibiotic stress. Mid-log-phase cells were grown in either the absence or presence of various antibiotics (cefotaxime, 100 μg/ml; ciprofloxacin, 0.4 μg/ml; ampicillin, 10 μg/ml; kanamycin, 50 μg/ml; and tobramycin, 25 μg/ml) in a 96-well microtiter plate, and growth was monitored using the absorbance of tetrazolium dye (0.02%) at 490 nm. Growth kinetics were monitored for 5 h, and the OD was plotted against time. The OD490 was normalized to zero with respect to the first reading. The average readings from three independent replicates were plotted. Both strains BW25113 ccdF and BW25113 ccdO157 show protection from cell death upon antibiotic exposure compared to the control strains, BW25113 ccdInactive and BW25113.