The dynamics of ultrastructural changes during Entamoeba invadens encystation

Entamoeba histolytica infection causes amoebiasis, which is a global public health problem. The major route of infection is oral ingestion of E. histolytica cysts, cysts being the sole form responsible for host-to-host transmission. Cysts are produced by cell differentiation from proliferative trophozoites in a process termed 'encystation'. Therefore, encystation is an important process from a medical as well as a biological perspective. Previous electron microscopy studies have shown the ultrastructure of precysts and mature cysts; however, the dynamics of ultrastructural changes during encystation were ambiguous. Here, we analysed a series of Entamoeba invadens encysting cells by transmission electron microscopy. Entamoeba invadens is a model for encystation and the cells were prepared by short interval time course sampling from in vitro encystation-inducing cultures. We related sampled cells to stage conversion, which was monitored in the overall population by flow cytometry. The present approach revealed the dynamics of ultrastructure changes during E. invadens encystation. Importantly, the results indicate a functional linkage of processes that are crucial in encystation, such as glycogen accumulation and cyst wall formation. Hence, this study provides a reference for studying sequential molecular events during Entamoeba encystation.