[Ultramicroscopic structure of the cyst wall of Entamoeba invadens, E. histolytica and E. coli]

The ultrastructure of the wall of E. invadens cysts induced in axenic cultures was compared by transmission electron microscopy of thin sections, with that of E. histolytica and E. coli cysts obtained from feces of human asymptomatic carriers. The cyst wall of the three species studied had similar ultrastructural features; in all, the wall was composed mainly by the aggregation of filaments adjacent to the plasma membrane. The cytoplasmic components which might be involved in the synthesis and deposit of the cyst wall of E. invadens appear to be different to those of E. coli and E. histolytica cysts.