<i>S. pneumoniae</i> response to oxidative stress.

<p>(<b>A</b>) Paraquat killing of the <i>S. pneumoniae</i> wild-type (D39) and Δ<i>sodA</i> mutant grown in CDM + 1 µM Mn(II) (white), and <i>S. pneumoniae</i> (D39) grown in 100 µM Zn(II):100 µM Mn(II) (black) or 100 µM Zn(II):1 µM Mn(II) (light gray) conditions. Survival was calculated as a percentage of c.f.u. after 30 minutes paraquat challenge compared to 30 minutes without challenge. The experiment was performed with 3 independent biological samples and data are the means (± SEM). The statistical significance of the differences in mean survival was determined by a two-tailed unpaired <i>t</i>-test (n.s. corresponds to not significant, * corresponds to <i>P</i> value < 0.05, and **** P value < 0.0001). (<b>B</b>) <i>S. pneumoniae</i> D39 mRNA transcription levels were examined after growth in CDM + 1 µM Mn(II) or 100 µM Zn(II):1 µM Mn(II). Real-time RT-PCR data for the indicated conditions were normalized against those obtained for the 16S rRNA control. Data are means (± SEM) of at least three biological replicates. The statistical significance of the differences in relative transcription level was determined by a two-tailed unpaired <i>t</i>-test (* corresponds to <i>P</i> value < 0.05, and ** to <i>P</i> value < 0.01). (<b>C</b>) <i>S. pneumoniae</i> D39 (filled) and Δ<i>sodA</i> (open) were grown in CDM supplemented with 1 µM Mn(II) until an A₆₀₀ of 0.3 was reached. Cells were washed in CDM and then inoculated to an A₆₀₀ of 0.05 in CDM consisting of in CDM + 1 µM Mn(II) (circle) or 300 µM Zn(II):1 µM Mn(II) (square). Data are means (± SEM) A₆₀₀ measurements from three independent biological experiments. Error bars, where not visible, are overlapped by the data points.