Mechanical strategies to avoid interspecies competition in trypanosomes

• Applicant: Professor Dr. Markus Engstler
• Subject Area: Parasitology and Biology of Tropical Infectious Disease Pathogens
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 491920625

Like all living beings, parasites must adapt optimally to an ecological niche. In the case of parasites, this niche is by definition hostile, as the host has developed defence strategies against the invader. Furthermore, the host is often infested by more than one parasite species, so that competition between parasites for the same infection niche can occur. Accordingly, avoiding interspecific competition is an important strategy for the evolutionary success of parasitism. We postulate that adaptations to the physics of the microenvironment play a crucial role in this process. African trypanosomes are unicellular parasites that extracellularly colonise the body fluids of their hosts. Interestingly, two closely related species, T. brucei and T. congolense, can colonise quite different niches in the same host, namely tissue interstitial spaces and the peripheral capillary system. Both parasite species differ only slightly in their body architecture, but significantly in their swimming behaviour and their ability to attach to host cells. The results from the first funding period support the “interspecies competition avoidance” hypothesis. T. brucei and T. congolense greatly differ in their ability to successfully steer in crowded, confined and flowing environments. Three key insights from the first funding period have been most important and will be studied further during the second funding phase: (1) Trypanosomes exert very little mechanical force on their surrounding microenvironment. 2) We found that the trypanosome cell body is far more elastic than expected and can adopt a stretched shape in high-viscosity environments. This finding impacts the patterns of flagellar beating but does not significantly affect the swimming velocity of the parasites. (3) We observed that while trypanosomes can successfully navigate through the interstitium of mature tissue models, they are unable to traverse in vitro collagen networks of similar or lower density. These discoveries have substantially altered our understanding of trypanosome behaviour and we plan to further explore their biological consequences in the second funding period.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2332: Physics of Parasitism