Free-living amoebae belonging to the genus Acanthamoeba are the causative agents of infections such as amoebic keratitis (AK), granulomatous amoebic encephalitis (GAE) and cutaneous lesions. The mechanisms involved in the establishment of infection are unknown. However, it is accepted that the initial phase of pathogenesis involves adherence to the host tissue. In this work, we analysed surface molecules with an affinity for epithelial and neuronal cells from the trophozoites of Acanthamoeba castellanii. We also investigated the cellular mechanisms that govern the process of trophozoite adhesion to the host cells. We first used confocal and epifluorescence microscopy to examine the distribution of the A. castellanii actin cytoskeleton during interaction with the host cells. The use of drugs, as cytochalasin B (CB) and latrunculin B (LB), revealed the participation of cytoskeletal filaments in the adhesion process. In addition, to identify the proteins and glycoproteins on the surface of A. castellanii, the trophozoites were labelled with biotin and biotinylated lectins. The results revealed bands of surface proteins, some of which were glycoproteins with mannose and N-acetylglucosamine residues. Interaction assays of biotinylated amoebae proteins with epithelial and neuronal cells showed that some surface proteins had affinity for both cell types. The results of this study provide insight into the biochemical and cellular mechanisms of the Acanthamoeba infection process.

Phenolic compounds, packaged within vesicles known as physodes, are a major cytoplasmic constituent of eggs and zygotes of the Australasian fucoid Hormosira banksii. Physode movement in early life stages of Hormosira is described. We have used the cytoskeletal inhibitors cytochalasin B, latrunculin B and nocodazole added during different stages of development to investigate the role of the cytoskeleton in movement of these vesicles to regions of active wall formation in the growing rhizoid tip and the plane of cytokinesis prior to cell division. Actin inhibition prevented polarization, cross-wall formation and physode movement. When microtubules were disrupted polarization was still possible, but cross-wall formation and physode movement were prevented. Both actin microfilaments and microtubules are necessary to move physodes to regions of accumulation and active wall formation.