About Giardia

 
 

Giardia intestinalis is a zoonotic, parasitic protist with a complex microtubule cytoskeleton critical for its two life cycle stages, the “trophozoite” and the “cyst”.  Giardia cysts are ingested from contaminated water or food, and then “excyst” into flagellated trophozoites in the animal host.  Trophozoites attach to the intestinal villi using a cytoskeletal structure termed the ventral disc; attachment is critical to avoid peristalsis. Detached trophozoites later “encyst” before leaving the host. Cysts persist in the environment where they often contaminate potable water sources and infect new hosts.


Giardia’s complex microtubule (MT) cytoskeleton is critical for motility, attachment, intracellular transport, cell division, and encystation/excystation. Rather than any specific virulence factor, the cytoskeleton itself can be considered the etiologic agent of giardiasis. Beyond its clinical relevance, the study of giardial cytoskeletal biology also informs basic cell biology, molecular biology and cellular evolution.


The MT cytoskeleton of Giardia consists of both unique MT-based structures (the median body, ventral disc, funis and cytoplasmic axoneme-associated elements) and MT-based structures commonly found in flagellated protists (eight flagella and two mitotic spindles). This elaborate MT cytoskeleton creates a stable scaffold for cell shape, cell polarization, and intracellular trafficking. Dynamic cytoskeletal functions include: attachment, motility, mitosis and cell division, and encystation/excystation.


 

an insider’s guide to giardial biology

ventral disc

median body

 
 

eight flagella

two spindles

funis

novel elements

Giardia intestinalis is the most common cause of protozoan intestinal infection worldwide.

Due to the lack of concerted research efforts, giardiasis has been designated as a “neglected disease” by the World Health Organization (WHO).











Giardia’s MT cytoskeleton

 

ventral disc

median body

two spindles

eight flagella