Blastocystis - Classification

Classification

The appropriate classification of Blastocystis has only recently been resolved. The original description of Blastocystis was as a yeast due to its yeast-like glistening appearance in fresh wet mounts and the absence of pseudopodia and locomotion. This was then contradicted by Zierdt, who reclassified it under subphylum Sporozoa, based on some distinctive protistan features of the Blastocystis cell, such as the presence of nuclei, smooth and rough endoplasmic reticulum, Golgi complex, and mitochondrion-like organelles. Its sensitivity to antiprotozoal drugs and its inability to grow on fungal media further indicated that it was a protozoan.

However, major revisions were made to its classification. An analysis of gene sequences was performed in 1996, which placed it into the group Stramenopiles. Other Stramenopiles include brown algae, mildew, diatoms, the organism that caused the Irish potato famine, and the organism responsible for Sudden oak death disease. However, the position of Blastocystis within the stramenopiles remains enigmatic.