(C) The structure of the dpr and metQIN promoters. -10 and −35 regions of the promoters are shown by the boxes. The start codon is labeled by blod fonts. The predicted PerR-box is underlined. The effects of H2O2 on the transcriptional regulation were tested. Bacteria were stimulated by 10 μM H2O2

for 10 min, the expression levels of dpr and metQIN were analyzed by qRT-PCR. As shown in Figure 4A, dpr and metQIN was obviously induced in SC-19 but not in ΔperR (cultured in TSB). Then, the EGFP reporter strains were check details used, the MFI of strains SC-19:EGFP and ΔperR:EGFP in chemical defined medium (CDM) was measured. As shown in Figure 4B, for the strain SC-19:EGFP, growth in medium with 50 μM zinc and 50 μM manganese led to a low green fluorescence MAPK inhibitor level, and no obvious induction by H2O2 (10 μM) could be detected.

In contrast, when grown in medium with 50 μM zinc and 50 μM iron, SC-19:EGFP expressed a relatively high level of EGFP, and the MFI was about two-fold higher after induction by H2O2 for 1 h. The MFI of strain ΔperR:EGFP was high and had no significant change in each condition. These results suggest that PerR regulated the target operons by binding to the promoter region, and the derepression was induced by H2O2 and influenced by metal ions. Figure 4 H 2 O 2 and metal ions affect the expression of the PerR regulon. (A) Relative transcript levels of dpr and metQIN after 10 μM H2O2 stimulating. (B) Expression of EGFP in strains SC-19 and ΔperR in the CDM supplemented with different metal ions. The cells were grown to mid-log phase in the basal CDM with 50 μM Zn2+ and 50 μM Fe2+ or Mn2+ and treated with or without 10 μM H2O2 cAMP 4 times in every 15 min. The final mean fluorescence intensity (MFI) was calculated

by each sample’s MFI deducting the MFI of negative control (no EGFP inserted SC-19). Roles of dpr in H2O2 resistance in S. Suis H2O2 sensitivity analysis suggested that PerR was involved in oxidative stress response and we have found that dpr was directly regulated by PerR in S. suis. dpr encodes a Selonsertib nmr peroxide resistance protein, previous study has found that dpr mutant was highly sensitive to H2O2[24]. To test the role of dpr in H2O2 resistance, the dpr gene was inactivated in strains SC-19 and ΔperR. The resultant mutant strains Δdpr and ΔperRΔdpr were subjected to the H2O2 sensitivity assay. Both dpr mutant strains exhibited <1% survival after incubation with 10 mM H2O2 (Figure 2B). Inactivation of dpr led to near loss of H2O2 defensive capability in both Δdpr and ΔperRΔdpr strains. However, there was no obvious difference in the survival rate between Δdpr and ΔperRΔdpr, suggesting that the increased H2O2 resistance of the perR mutant probably results of the derepression of dpr. Role of methionine in H2O2 resistance in S. Suis Expression of the methionine ABC transporter metQIN was upregulated in the ΔperR, therefore, methionine uptake may have been increased in the mutant.