Trends in Parasitology
ReviewBeyond Blood: African Trypanosomes on the Move
Section snippets
Parasites Are Motile and Manoeuvre to Spread in Their Hosts
Parasites are expert travellers. They explore their environment by swimming or crawling, to infest their habitats once the destination has been reached. At first sight this seems trivial. But do we really know how parasites navigate, and how the life conditions in the rather diverse microenvironments influence their motion? When compared to free-living species, parasites thrive in small worlds. Their host habitats are secluded, largely homeostatic, and thus fairly predictable. Furthermore,
The Trypanosome Swimming Apparatus
The structure of the T. brucei flagellum and its attachment to the cell body have been concisely reviewed 7, 8.
The basic morphological architecture is modified in a series of developmental stage transitions, possibly in order to adapt to specific niches of the host bodies. The dynamic extension of the microtubule corset allows the repositioning of the flagellar pocket with the connected basal body along the anterior–posterior axis. This changes the emergence point of the flagellum and its
The Cellular Waveform Describes the Dynamic Pleomorphism of Trypanosomes
The complex three-dimensional movement of the various trypanosome stages has been analysed in some detail. Cellular waveforms describe the combined, effective oscillatory and rotational actuation relevant to the characteristic locomotion of a specific morphotype 1, 2. The chirality of the attached flagellum determines the rotational motion of trypomastigotes, while the flagellar wave that is generated by axonemal oscillations deforms the attached, elastic cell body with characteristic
Lifelong Motion
As strictly extracellular parasites, African trypanosomes do not feature an immotile life cycle stage, which distinguishes them from, for example, Plasmodium, Trypanosoma cruzi or Leishmania. An active flagellum is always present, albeit varying in length from a few μm to several tens of μm. Hence, the most obvious function of transporting a cell through body fluids is accomplished with largely varying efficiency 1, 2.
Concluding Remarks
The apparently simple questions of parasitology, namely those related to life cycles, motile behaviour, or host niches, need some reconsideration (see Outstanding Questions). The precise mode of trypanosome annidation in the mammalian hosts, for example, or the impact of the ever-changing microenvironments on parasite swimming styles and performance, are poorly understood. The methods required to close those gaps, in a statistically sound manner, are available; however, standardised protocols
Acknowledgments
We are grateful to Ines Subota for sharing her tsetse expertise, and wish to thank Christian Reuter for helpful discussions. ME is supported by DFG grants EN305, GRK2157 (3D Tissue Models to Study Microbial Infections by Obligate Human Pathogens), and SPP1726 (Microswimmers – From Single Particle Motion to Collective Behaviour). ME is a member of the Wilhelm Conrad Roentgen Center for Complex Material Systems (RCCM).
Glossary
- Ectoperitrophic space
- the volume within insect midguts that is separated by the peritrophic matrix from the food bolus.
- Interstitial space
- contains the main part of extracellular body fluid and fills the spaces between cells and tissue-specific structures.
- Peritrophic matrix
- a dynamic extracellular sheet that lines the midgut of the tsetse fly and other insects.
- Proventriculus
- a muscular organ that is connected to the crop of some insects (such as the tsetse fly) and assists with the grinding of food.
References (64)
Composition and sensory function of the trypanosome flagellar membrane
Curr. Opin. Microbiol.
(2010)Hydrodynamic flow-mediated protein sorting on the cell surface of trypanosomes
Cell
(2007)Kinetics of linear rouleaux formation studied by visual monitoring of red cell dynamic organization
Biophys. J.
(2000)Trypanosoma brucei parasites occupy and functionally adapt to the adipose tissue in mice
Cell Host Microbe
(2016)- et al.
Tsetse fly evolution, genetics and the trypanosomiases – a review
Infect. Genet. Evol.
(2018) Flying tryps: survival and maturation of trypanosomes in tsetse flies
Trends Parasitol.
(2013)Asymmetric cell division as a route to reduction in cell length and change in cell morphology in trypanosomes
Protist
(2008)Meiosis and haploid gametes in the pathogen Trypanosoma brucei
Curr. Biol.
(2014)Proteomic analysis of intact flagella of procyclic Trypanosoma brucei cells identifies novel flagellar proteins with unique sub-localization and dynamics
Mol. Cell. Proteomics
(2014)The paraflagellar rod: a structure in search of a function
Biol. Cell
(1988)