Initial attempts to find a relationship through RNA analyses could not place it among the protozoa or fungi. Serious proposals were made to create a new phylum just for Blastocystis. It has not been until recently that careful molecular genetic studies have revealed its true relationship in the arcane world of taxonomy. We certainly did, for there were no known parasites of humans in this obscure category. Based on analyses of small-subunit ribosomal RNA, stramenopiles, green plants, red algae, animals, and alveolates separated from one another about 1 billion years ago.
Human parasite finds taxonomic home.
Well, it may sound like a taxonomic wastebasket, but it does give us a clue as to some close relatives of our enigmatic Blastocystis . The riboso mal RNA studies place Blastocystis closest to a flagellate protozoan called Proteromonas, a parasite of the intestinal tract of reptiles and amphibians. Blastocystis and Proteromonas are both enteric parasites, have tubular christae in their mitochondria, and may have some similarities in reproductive cycles. The investigators think that Blastocystis had flagella at one time but lost this feature during its evolution. Unfortunately, probably very little.