Ultrastructural insights into morphology and reproductive mode of Blastocystis hominis.

To understand well the morphology and reproductive mode of Blastocystis hominis, with the help of transmission electron microscopy and scanning electron microscopy the ultrastructural details of B. hominis from fresh diarrheal specimens and cultured strains were observed. In both fecal samples and culture conditions, there were vacuolar and granular forms. In diarrhea, it exists in multivacuolar, avacuolar, and amoeboid forms. In the in vitro culture, vacuolar form could transform to granular form. The most commonly noticed structure on the cell surface was surface coat with diversity in appearance (the funiform, lamellar, filiform, and floccose in different thickness) and distributions. Three modes of reproduction were confirmed, they were binary fission, plasmotomy, and budding. Under the impact of host's response, the ultrastructures of surface coat, nucleus, and mitochondrion-like organelle sometimes changed.