ELECTRON-MICROSCOPY OF SURFACE-STRUCTURES OF BLASTOCYSTIS SP FROM DIFFERENT HOSTS

Samples of Blastocystis sp. obtained from humans, monkeys, pigs and ch ickens were examined by scanning electron microscopy and transmission electron microscopy to compare surface structures. The surface coat of Blastocystis sp. cells from each host species showed some morphologic al variations, but these were not sufficiently different to allow judg ement to be made on speciation. The surface structure morphology appea red similar for samples of Blastocystis sp. from the same host species . The surface coat of the cultured human isolate of B. hominis was muc h thinner than that of cells from fresh human faecal material, and the cell surface appeared to be smoother and without the small projection s seen in the fresh forms. Bacteria were frequently found in associati on with the surface coat of Blastocystis sp. from all fresh faecal mat erial. Possible functions of the surface coat, especially in relation to protection against osmotic shock, are discussed.