FIG. 4.

(A) Threshold level of ClfB expression required for platelet activation. L. lactis ClfB cultures induced with increasing concentrations of nisin were incubated with PRP, and the lag time to activation was measured. (B) Threshold level of bacterial cells required for platelet activation. Doubling dilutions of fully induced L. lactis ClfB (OD₆₀₀ of 1.6) were added to platelets, and the lag time to activation was measured. Asterisks indicate no activation after 25 min. The percent aggregation is shown above the error bars.