Fig. 5

The effect of Zn and Cu treatment on the resistance of A. baumannii to oxidative stress. The effect of (a) 40 μM paraquat and (e) 160 μM H₂O₂ on A. baumannii strain ATCC 17978 grown in the presence of 400 μM Zn, 400 μM Cu, 400 μM Zn + 400 μM Cu, or without added metal ions, was determined by measuring the optical density at 600 nm (OD₆₀₀). The growth delay between untreated (UT) and paraquat- or H₂O₂-treated cells was examined by comparing the EC₅₀ under each relevant metal ion stress condition. Statistical analyses were performed using a one-way ANOVA. b The total SOD activity of mid-log phase cells (untreated, 400 μM Zn, 400 μM Cu or 400 μM Zn + 400 μM Cu) was determined. Data were corrected for total protein content, followed by normalisation to untreated cells. Statistical analyses were performed using a Student’s t-test. The mRNA transcription levels of (c) Cu-Zn superoxide dismutase (Cu-Zn-SOD; A1S_3143), (d) Fe/Mn superoxide dismutase (Fe/Mn-SOD; A1S_2343) were determined by qRT-PCR. The transcription levels examined in the presence of 400 μM Zn, 400 μM Cu or 400 μM Zn + 400 μM Cu were corrected to untreated cells following internal normalisation to GAPDH. The data are the mean of at least biological triplicates (± SEM). Statistical analyses were performed by one-way ANOVA using Dunnett’s posttest. For all statistical analyses; ns = not significant, * = p < 0.05, ** = p < 0.01, *** = p < 0.001 and **** = p < 0.0001