"Structure and Function of Trypanosoma Brucei" is a good example of a paper on infectionsOne of the commonly seen Trypanosoma brucei species is Trypanosoma brucei rhodesiense. Another common species of Trypanosomes that infects mammals is Trypanosoma brucei gambiense. The third species that is a member of the Trypanosoma brucei species is a species called Trypanosoma brucei brucei. These parasites are transmitted between mammalian hosts by the Glossina spps. Trypanosomes cause African sleeping sickness in 36 sub-Saharan countries (Mathews 2005). Cattle and game animals are also infected, and the resulting disease is called Nagana.
In mammals, Trypanosomes exist freely in the bloodstream and can evade host immune responses using an antigenic variation. To evade host immune responses, trypanosomes surface membrane contain 107 copies of invariant surface glycoproteins (VSG) that are periodically replaced as the host immune system synthesizes antibodies against them. Trypanosomes have unique structures that serve particular functions and help them survive within the host and to proliferate and cause disease. Pellicle (cytoskeleton) Figure (1) below shows structures found in Trypanosome cells. Trypanosomes have an elongated body that is covered with a microtubule cytoskeleton (pellicle).
The microtubule cytoskeleton maintains the cell’ s architecture and consists of sub-pellicular microtubules. Sub-pellicular microtubules are linked to the plasma membrane and are interlinked with each other by MAPs (microtubule-associated proteins) and are found in close association with low molecular weight CAP 15 and CAP 17 (Vedrenne et al. 2002). CAP 15 and CAP 17 induce morphological changes during the cell cycle and result in asymmetric cytokinesis. Flagellar Pocket The flagellar pocket is a specialized domain on the plasma membrane that forms the point of exocytosis or endocytosis. It has an asymmetrical shape which correlates with the location of the Golgi complex and proposal body.
The flagellar pocket is the point of exit of the flagellum. The collar and collarette are boundary structures found on the flagellar packet and are closely associated with the entry and exit of the flagellum. Figure 1: A diagram showing the various structures of Trypanosoma brucei Flagellum Each Trypanosome cell has a single flagellum which originates from the basal body and is linked to the mitochondrial genome by a mitochondrial membrane. It has the characteristic axonemal structure and with a crystalline PFR (Paraflagellar rod) rod.
In straight flagella, the PFR lattice repeats every 56 nanometers along the axoneme. It has an undulating membrane that is irregular, finlike, and thin as shown in figure (2) below. The undulating membrane plays a role in the movement of the parasite. The flagellum interacts with the sub-pellicular cytoskeleton at the flagellum attachment zone with the aid of trypanin to direct the trypanosome cell to the desired location (Mathews 2005). Mitochondria The mitochondrion is an elongated structure that lacks cristae in the blood form.
The absence of cristae in mitochondria signifies the ability of the parasite to generate energy by a series of glycolytic reactions using its glycosomes from the glucose-rich host blood (Mathews 2005). Procyclic trypanosome forms have cristae within their mitochondria and generate energy using their mitochondria.
FAO. 2014. African animal Trypanosomes. [Online] Available at http://www.fao.org/docrep/006/x0413e/x0413e02.htm [Accessed 06 November 2014]
Mathews, K.2005. The developmental cell biology of Trypanosoma brucei. Journal of Cell Science, 118, 283-290. [Accessed 06 November 2014]
Vedrenne, C., Giroud, C., Robinson, D.R., Besteiro, S., Bosc, C., Bringaud, F., and Baltz, T. 2002. Two related sub-pellicular cytoskeleton- associated proteins in Trypanosoma brucei stabilize microtubules. Mol Cell Biology, 13(3), 1058- 70. [Accessed 06 November 2014]