Light micrograph of an immature parasitic Entamoeba coli binucleated (containing two nuclei) cyst. Entamoeba coli is a non-pathogenic species of amoebae that can colonize the human gastrointestinal tract. Cysts of Entamoeba coli are usually spherical and measure between 10 to 35 micrometres. Mature cysts typically have eight nuclei but may have as many as sixteen or more.