Figure 1.

TpxD scavenging activity is crucial for pneumococcal global response to high H₂O₂ levels. Seven genes identified in the microarray to be affected by 1 mM H₂O₂ were selected for further examination by relative RT-PCR. D39 and TpxDC58S mutant were grown anaerobically to OD₆₂₀ = 0.25 and then challenged with 100, 250, or 1000 μM H₂O₂ for 40 min. Control cultures were grown without (w/o) the addition of H₂O₂. Values are the mean of duplicate determinations of at least two independent experiments, and were normalized to the expression level of the relevant unchallenged strain (D39 or TpxDC58S). Bars indicate standard deviation. Significant alterations in gene expression compared to bacteria grown without H₂O₂ were determined using Student's t-test.