Figure 3.

SrtR contributes to oxidant and high-temperature tolerance in Streptococcus suis. The role of srtR was evaluated by comparing the same background strains (DN13, DN13:ΔsrtR vs. DN13:CΔsrtR and DN13- srtR, SS9-P10:ΔsrtR vs. SS9-P10 as well as SS9-P10:CΔsrtR) with or without functional srtR. All experiments in this part were conducted in duplicate and repeated three times. Values were expressed as mean percentages with standard deviation. One-way analysis of variance (ANOVA) with Kruskal-Wallis test was used to assess oxidative and thermal stress assays. Plasmid-encoded srtR significantly increased resistance to H₂O₂ challenge in SrtR-deficient strains; DN13, DN13:ΔsrtR, and SS9-P10-ΔsrtR (A). Growth at 42°C was significantly improved by the introduction of plasmid-encoded srtR into SrtR-deficient strains; DN13:ΔsrtR, and SS9-P10-ΔsrtR (B). Survival data of DN13 and SS9-P10 at 42°C were identical to those displayed in Figure 2B, as thermal tolerance assays with DN13, the mouse-adapted strains, and engineered strains were conducted at the same time. **P < 0.01.