FIG 5.

SavRS represses the expression of virulence genes hla and efb. (A) The savRS mutant strain exhibited increased hemolytic activity. The hemolytic activity assay was performed in 3% sheep erythrocytes. (B) The hemolytic activity was determined by absorption of supernatants at 543 nm. The percentage of hemolytic activity was calculated relative to the positive control, which was regarded as 100% hemolytic activity. ****, P < 0.0001. (C) The transcript levels of some virulence genes in the WT and the savRS mutant strains by qRT-PCR assay. *, P < 0.05; **, P < 0.01; ***, P < 0.001. (D) Analysis of the mRNA half-life in the WT, the savRS mutant, and the savRS complemented strains. (E) The growth-phase-dependent transcription of hla and hlb in the WT and the savRS mutant strains. **, P < 0.01; ***, P < 0.001; ****, P < 0.0001. (F) The β-galactosidase activity under the control of the hla promoter and efb promoter in WT and savRS mutant strains. **, P < 0.01. (G) Comparison of the protein expression levels of WT and savRS mutant strains by Western blotting. (H) Analysis of mRNA levels in hemolytic activity assay. The strains were incubated with 3% sheep erythrocytes for 20 min, the cells were collected, and the mRNA levels were analyzed by qRT-PCR. **, P < 0.01.