Freeze-etching observations of trophozoites of pathogenic Entamoeba histolytica

Pathogenic Entamoeba histolytica trophozoites were studied by the freeze-etching (FE) technique of electron microscopy. Surface replicas of intact cell membranes were highly convoluted with numerous invaginations, evaginations, and undulations. Spherical depressions and elevations varying from 0.5 μ to 1.0 μ in diameter were commonly present on the external cell membrane and appeared to represent an extracellular secretory mechanism of trophozoites. Cleaved surfaces of amebae exhibited a granular and lumpy cytoplasm in which there were many vesicles and vacuoles that ranged in diameter from 0.2 μ to 9.0 μ. Some vacuoles contained tightly enveloped bacteria, while others contained bacteria and host cytocomponents. Occasional vesicles and vacuoles appeared to be fused to each other.