Efficient Liquid Media for Encystation of Pathogenic Free-Living Amoebae.

Pathogenic , , and , are distributed worldwide. They are causative agents of primary amoebic meningoencephalitis or acanthamoebic keratitis in humans, respectively. Trophozoites encyst in unfavorable environments, such as exhausted food supply and desiccation. Until recently, the method of encystation used solid non-nutrient agar medium supplemented with heat-inactivated ; however, for the amoebic encystment of spp., a defined, slightly modified liquid media is used. In this study, in order to generate pure cysts, a liquid encystment medium (buffer 1) modified from Page's amoeba saline was applied for encystation of . cysts were well induced after 24 hr with the above defined liquid encystment medium (buffer 1). This was confirmed by observation of a high expression of differential mRNA of and actin genes in trophozoites. Thus, this liquid medium can replace the earlier non-nutrient agar medium for obtaining pure cysts. In addition, for cyst formation of spp., buffer 2 (adjusted to pH 9.0) was the more efficient medium. To summarize, these liquid encystment media may be useful for further studies which require axenic and pure amoebic cysts.