FIG 5.
VraSRSS indirectly regulated expression of the CPS biosynthesis gene cluster in SS2. (A) Schematic diagram of the genetic organization of the CPS synthesis and the sialic acid synthase clusters. The arrows indicate the direction of transcription. (B) Expression levels of cps2C, cps2F, and neuB in ZY05719, ΔvraSRSS, and CΔvraSRSS strains were measured by qRT-PCR. The unpaired two-tailed Student's t test was used for statistical analysis (ns, P > 0.05; ***, P < 0.001). (C) Transmission electron micrographs of the ZY05719, ΔvraSRSS, and CΔvraSRSS strains. The scale bars indicate the magnification size. (D) Photomicrographs of the capsules of the ZY05719, ΔvraSRSS, and CΔvraSRSS strains stained with crystal violet (1,000×). (E) VraRSS indirectly regulated the CPS biosynthesis gene cluster. Either the cps or neu promoter region could be shifted by the recombinant VraRSS protein in EMSAs. DNA probes containing the yvqFSS operon promoter region were used as a positive control, and fragments amplified from 16S rRNA served as a negative control.