Cap Formation Induced by Concanavalin A in Pathogenic Free-living Amoebae

Morphological differences in cap formation were found when trophozoites of different free-living amoebae were treated with the lectin Concanavalin A, which resulted in a rapid redistribution of certain surface components to form small clusters and membrane-folded structures of diverse sizes. Acanthamoeba castellanii, Acanthamoba polyphaga and Naegleria lovaniensis exhibited characteristic caps, however, in A. castellanii this structure was larger and included several folds of the plasma membrane; furthermore, some of these caps had vacuoles containing a fi bro granular content. In contrast, the caps formed by A. polyphaga and N. lovaniensis lacked vacuoles. Regarding Naegleria fowleri, the trophozoites did not produce a defi ned cap, and only small patches of lectin-bound surface receptor complexes were observed at one pole of the cell body. In the free-living amoebae studied, it was not possible to correlate the shape and size of cap with pathogenicity.