A Microbial Biorealm page on the genus Trypanosoma brucei
Higher order taxa
Kingdom: Eukaryota; Phylum: Euglenozoa; Order: Kinetoplastida; Family: Trypanosomatidae; Genus: Trypanosoma; SubGenus: Trypanozoon; Species: Trypanosoma brucei
Genus: Trypanosoma Species: brucei Sub-species: Trypanosoma brucei brucei,Trypanosoma brucei gambiense, Trypanosoma brucei rhodesiense,Trypanosoma brucei TREU927.
Description and Significance
The eukaryotic Trypanosoma brucei is one of the parasitic species from the Trypanosoma genus. It exists in two forms: an insect vector, and once inside the bloodstream, a mammalian host. Once inside the mammalian host, it has the ability to inflict African trypanosomiasis, (sleeping sickness). T. brucei exists as its insect vector in the tsetse fly. Once the fly bites a mammal, the microbe enters the bloodstream where it transforms into the mammalian host form, and is then capable of mutating and invading the central nervous system.
The complete genome of T. brucei has been sequenced; this is important because it is key information that is used to research possible cures for Trypanosomiasis.
Describe the appearance, habitat, etc. of the organism, and why it is important enough to have its genome sequenced. Describe how and where it was isolated. Include a picture or two (with sources) if you can find them.
Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?
The genome of T. brucei has surface antigens that allow the bacteria to escape from being noticed by the immune system. T. brucei is capable of continuously changing the expression of these antigens to effectively hide from antibodies.
Cell structure and metabolism
In general, the cellular structure of Trypanosoma brucei is similar to all other eukaryotes. There are however, a few differences. T. brucei's cell surface has, (in addition to its surface antigens), a thick layer of proteins, called Variant Surface Glycoprotein (VSG's) genes. These allow the surface antigens to mutate, by switching variants. Having over 1000 VSG genes and psuedogenes, T. brucei is able to switch variants frequently. Trascription occurs one gene at a time, from one of many telomeric VSG expression sites. In order to switch an active VSG gene, DNA rearrangements must occur, to switch the old VSG gene with a new one. Using the bloodstream form of T. brucei, scientists in the Netherlands discovered that telomere exchange, thought to be rare, was indeed occuring. The scientists marked a VSG gene with a hygromycin resistance gene, allowed the gene to undergo variation, and selected switched Trypanosomes. The drug sensitivity and polymerase chain reactions (PCR), revealed that telomere exchange had taken place.
T. brucei also has unusual Citric Acid Cycles and a single large mitochondria. In the insect vector host, the Citric Acid Cycle is not used to generate energy; rather parts of the Citric Acid Cycle are suggested to be used for: acetyl-CoA transport into cytosol, degradation of proline and glutamate to succinate, and the formation of malate. The Citric Acid Cycle is not functioning as a cycle itself, but parts of its pathways are being used in T. brucei.
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Enter summaries of the most recent research here--at least three required
- Frank SA, Barbour AG. "Within-host dynamics of antigenic variation". 'Infection Genetics and Evolution'. 2006. p. 146-146.
- Lythgoe KA, Morrison LJ, Read AF, Barry JD. "Parasite-intrinsic factors can explain ordered progression of trypanosome antigenic variation". 'Proceedings of The National Academy of Sciences of The United States of America'. May 8 2007. p. 8095-8100.
- Taylor JE, Rudenko G. 'Switching trypanosome coats: what's in the wardrobe?'. 2006 Aug 14.
- Rudenko G, McCulloch R, Dirks-Mulder A, Borst P. 'Telomere exchange can be an important mechanism of variant surface glycoprotein gene switching in Trypanosoma brucei.'. 1996 Sep.
- van Hellemond JJ, Opperdoes FR, Tielens AG. "The extraordinary mitochondrion and unusual citric acid cycle in Trypanosoma brucei.". 2005 Nov.