Figure 1.

Nonsense mutation in spr1178 and reduced accumulation of reactive oxygen species induced by bactericidal antibiotics. Drug-induced reactive oxygen species accumulation in S. pneumoniae. The DCF-DA fluorescence signals of the S. pneumoniae R6^{SmR, 2x2b1a-M2} (green bars) and R6^{SmR, 2x2b1a, spr1178-M2} (yellow bars) transformants following exposure to (a) 0.1 μg/ml penicillin, (b) 4.0 μg/ml ciprofloxacin, (c) 400.0 μg/ml kanamycin, (d) 6.0 μg/ml chloramphenicol, and (e) 0.25 μg/ml tetracycline were measured prior to antibiotic exposure (time zero) and 1 hour, 2 hours, and 3 hours following addition of the antibiotics. The DCF-DA fluorescence signals of the S. pneumoniae R6^{SmR, 2x2b1a-M2} (blue bars) and R6^{SmR, 2x2b1a, spr1178-M2} (orange bars) transformants untreated cultures measured at each time point are indicated as control. Results are the average of at least three independent experiments. RFU, relative fluorescence units.