Showing posts with label protozoa. Show all posts
Showing posts with label protozoa. Show all posts

Friday, September 28, 2012

Brazilian Society of Protozoology - 2012 meeting

It's time to bone up on my Portuguese! Off to

XXVIII ReuniĆ£o Anual da Sociedade Brasileira de Protozoologia

in Caxambu, Brazil tomorrow.

Giving keynote lecture on 3rd of October. Title of talk: "Blastocystis - friend or foe?"

The lecture is mainly based on thoughts presented in my recent paper: "Thinking Blastocystis Out of The Box" (PMID: 22704911) and output from our most recent studies.


Thursday, April 26, 2012

What is Blastocystis?

Intestinal parasites of humans can be divided into mainly helminths ('worms' including cestodes, nematodes and trematodes), and single-celled eukaryotic organisms. Most single-celled intestinal parasites belong to one of four main groups:
  • Archamoebae or Amoeboids (e.g. Entamoba, Iodamoeba, Endolimax)
  • Ciliates (e.g. Balantidium)
  • Sporozoa (e.g. Cryptosporidium, Cyclospora, Cystoisospora; even microsporidia)
  • Flagellates (e.g. Giardia, Chilomastix, Enteromonas, Pentatrichomonas, Retortamonas, Dientamoeba (unflagellated flagellate!))
Traditionally, these four groups have been referred to as protozoa.

However, the most common, single-celled intestinal parasitic eukaryote, Blastocystis, does not belong in any of these four categories. Taxonomically, Blastocystis belongs to the heterogeneous group of Stramenopiles, which includes slime nets, diatoms, water moulds and brown algae. Most stramenopiles are free-living organisms. Blastocystis is an atypical stramenopile not only as this group is named for the straw-like tubular hairs on the flagella and sometimes the cell body - Blastocystis has no flagella and lacks any tubular hairs - but also due to its parasitic nature.

Often, Blastocystis is referred to as a 'protozoon', although 'protist' is more appropriate. Protists can be defined basically as any eukaryote that is not a plant, an animal or a fungus.

One of the closest relatives of Blastocystis identified to date is Proteromonas lacertae, a parasite of reptiles.

Interestingly, Proteromonas does have flagella and hairs on the cell body. For comparison, the image below shows Blastocystis (culture) - appearing almost amoeboid, only with very limited morphological hallmarks (note examples of binary fission and the eccentrically located nuclei and mitochondrion-like organelles).

Blastocystis is one of two Stramenopiles known to infect humans, the other being Pythium insidiosum, which has been associated with keratitis and dermatological lesions mainly in SE Asia.

Other organisms with close relation to Blastocystis include Karotomorpha, Cepedea, Protoopalina and Opalina.

For further information, please visit

Silberman, J., Sogin, M., Leipe, D., & Clark, C. (1996). Human parasite finds taxonomic home Nature, 380 (6573), 398-398 DOI: 10.1038/380398a0  

HOEVERS, J., & SNOWDEN, K. (2005). Analysis of the ITS region and partial ssu and lsu rRNA genes of Blastocystis and Proteromonas lacertae Parasitology, 131 (2), 187-196 DOI: 10.1017/S0031182005007596  

Kostka, M., Cepicka, I., Hampl, V., & Flegr, J. (2007). Phylogenetic position of Karotomorpha and paraphyly of Proteromonadidae Molecular Phylogenetics and Evolution, 43 (3), 1167-1170 DOI: 10.1016/j.ympev.2006.11.002