RyhB activates CPS biosynthesis. (A) Comparison of CPS levels in WT, ΔryhB, Δfur, and Δfur ΔryhB strains. Bacterial strains were grown in LB medium at 37°C with agitation. After 16 h of growth, the bacterial glucuronic acid content was determined. *, P < 0.001 compared with WT. (B) WT strains carrying the vector control (pETQ) or pETQ-ryhB were grown in LB with 100 μM IPTG to induce ryhB expression. *, P < 0.001 compared with WT strains carrying pETQ.