Entamoeba invadens and E. histolytica: separation and purification of precysts and cysts by centrifugation on discontinuous density gradients of Percoll.

The different cell forms in the life cycle of Entamoeba invadens (trophozoites, precysts, and cysts) were rapidly and quantitatively separated on density step gradients of polyvinylpyrolidone-coated colloidal silica particles (Percoll). With this method, the gradual process of encystation by E. invadens trophozoites could be monitored. Percoll gradients were also efficient in separating trophozoites of Entamoeba histolytica and bacteria. After purification on Percoll, trophozoites display no evidence of damage when examined by light microscopy and no loss in viability as judged by their ability to multiply.