Parental Δku80 strain tachyzoites switched normally to the bradyzoite cyst stage based on expression of cytosolic green fluorescent protein (GFP) under control of the bradyzoite stage-specific LDH2 gene promoter (11) and on the development of the cyst wall structure that surrounds the bradyzoites as assessed by Dolichos biflorus agglutinin (DBA) lectin staining of the major cyst wall protein CST1 (12) (Fig. 2A). The gene discussed is CST1; the disease is cyst.