Encystment and Excystment Processes in Acanthamoeba castellanii: An Emphasis on Cellulose Involvement

The free-living amoeba Acanthamoeba castellanii is a unicellular eukaryote distributed in a wide range of soil or aquatic environments, either natural or human-made, such as rivers, lakes, drinking water, or swimming pools. Besides its capacity to transport potential pathogens, such as bacteria or viruses, Acanthamoeba spp. can have intrinsic pathogenic properties by causing severe infections at the ocular and cerebral level, named granulomatous amoebic encephalitis and amoebic keratitis, respectively. During its life cycle, A. castellanii alternates between a vegetative and mobile form, named the trophozoite, and a resistant, latent, and non-mobile form, named the cyst. The cyst wall of Acanthamoeba is double-layered, with an inner endocyst and an outer ectocyst, and is mainly composed of cellulose and proteins. The resistance of cysts to many environmental stresses and disinfection treatments has been assigned to the presence of cellulose. The current review aims to present the importance of this glycopolymer in Acanthamoeba cysts and to further report the pathways involved in encystment and excystment.