A MULTIPLE FISSION-LIKE MODE OF ASEXUAL REPRODUCTION IN BLASTOCYSTIS-HOMINIS

A non-axenic and an axenic isolate of Blastocystis hominis have been i nduced to form cysts in vitro using an encystation medium. The morphol ogy of the parasite at different time points was observed by scanning electron microscopy. In day-2 cultures the cysts were spherical and ha d a non-uniform, coarse outer surface around the body. A deep, pore-li ke opening was seen in some of the parasites. Most of the cysts from d ay-4 and day-6 cultures ruptured, revealing small, uniformly sized sph erical bodies occurring in grape-like clusters. Acridine orange staini ng confirmed that these bodies were the progeny of Blastocystis homini s. A multiple fission-like reproduction process giving rise to many da ughter Blastocystis occurs within the cyst.