Background: Compared with many protists, Giardia lamblia has a simple
life cycle alternating between cyst and trophozoite. Most research on the molecular
biology of Giardia parasites has focused on trophozoites and the processes of
excystation and encystation, whereas cysts have attracted less interest. The striking
morphological differen... read moreces between the dormant cyst and the rapidly dividing and
motile trophozoite implies profound changes in the metabolism as the parasite encysts
in the host's intestine and excysts upon ingestion by a new host.