FIG. 4.

Degradation of β-toxin and β-toxoid by spent B. subtilis supernatants. Lactococcus lactis-produced β-toxin and β-toxoid cultures were incubated with spent supernatants of stationary-phase cultures of B. subtilis strains 168 and WB800. As a control, TY medium was used. (A) Typical Coomassie brilliant blue-stained polyacrylamide gel showing results of the degradation assay. The incubation time (T) in minutes is indicated. Left lanes show β-toxoid and β-toxin exposed to strain 168 culture supernatant; right lanes show β-toxoid and β-toxin exposed to strain WB800 culture supernatant. M, protein marker, 35-kDa band. (B) The amount of β-toxin/β-toxoid measured after 10 min was set to 100%. The remaining amounts of β-toxoid and β-toxin after 1 h were determined and plotted. Experiments were performed in duplicate; error bars depict standard errors.