ABSTRACT
The amebas causing meningoencephalitis in humans and lower mammals belong to Acanthamoeba and not Hartmannella. These two genera are also distinct serologically and nutritionally. The light microscopic features of trophozoites and cysts of free-living amebas should be supplemented with transmission and scanning electron microscopy. There are different proteins forming the cytoplasm of free-living amebas. These proteins may be detected and characterized by different variants of Immunoelectrophoresis. The immunoelectrophoretic profiles are useful for taxonomy and classification of genera and species. The cysts are very useful in classification of free-living amebas because there is no distinctive or specific features to differentiate genera and species. The most characteristic features of the cysts are the shape, the appearance of the wall, and the number and morphology of the pores. The nucleus is usually centrally located, relatively small, with a centrally placed nucleolus. An interesting feature is the sharp separation between the nuclear membrane and the cytoplasm.
