Fig. 1.

A Late com protein is required for comX transcription shutoff. Comparison of comC and comX expression in response to CSP in wild-type and comX⁻ cells confirms influence of ComX on comX expression. (Left) Promoter activities; (Right) apparent rates of transcription [expressed as relative luminescence unit (RLU) increase per arbitrary time unit] calculated at a given time point, t₁, by substracting RLU value at t₀ from RLU value at t₁, as previously described (12). CSP (100 ng/mL⁻¹) was added after 10-min incubation in C+Y (SI Materials and Methods). Strains used: (Upper) comC::luc R2002 (comX⁻) and R1960; (Lower) comX::luc R2256 (comX⁻) and R2250. CSP was added at 0 min.