RPS19 and cyst: Within 36 h, the fraction of DBA-positive vacuoles (indicative of bradyzoites) was reduced from 71.66 to 20.4%, in strong contrast to the Δss mutant, which displayed only a modest decline in cyst staining from 86 to 72.46% within the first 12 h and to 64% in 36 h) (figure 5).