<P> Some soil - dwelling plant parasitic nematodes, such as the soybean cyst nematode, or the potato cyst nematode form cysts as a normal part of their lifecycle . </P> <P> The composition of the cyst wall is variable in different organisms . The cyst walls of bacteria are formed by the thickening of the normal cell wall with added peptidoglycan layers whereas the walls of protozoan cysts are made of chitin, a type of glycopolymer . Nematode cyst walls are composed of chitin reinforced by collagen . </P>

When does the dormant cyst excyst in the human body