Fig. 2.

(A) The QS response of the domesticated and QS⁺ B. subtilis BD2833 (srfA-lacZ) and QS signal-deficient (QSS⁻) B. subtilis BD2876 (srfA-lacZ) was monitored by β-galactosidase activity. Cultures were incubated until the stationary phase with a range of concentrations of the ComX pheromone purified from recombinant E. coli ED367. Error bars represent the SE indicated for every time point. (B) Chromatograms were obtained after HPLC analysis of surfactin isolated from the spent media of the B. subtilis PS216 and PS 216ΔcomQ control cultures (no ComX) and cultures supplemented with 0.05 fraction purified ComX.