Trypanosome motility in blood and particle suspensions

Abstract

Motile microorganisms often navigate crowded and structurally complex environments, where surrounding obstacles can strongly influence locomotion. The bloodstream form of the flagellate parasite Trypanosoma brucei circulates in blood, a dense suspension of red blood cells (RBCs), yet the physical mechanisms governing its locomotion under such conditions remain poorly understood because direct experimental observations are challenging. Here, we combine numerical simulations with in vitro experiments to investigate trypanosome motility in concentrated RBC suspensions and in suspensions of spherical colloidal particles. Simulations reveal that the parasite swimming speed increases by up to 50% at RBC volume fractions comparable to those in blood. To identify the origin of this enhancement, we perform controlled studies in colloidal suspensions with particles of different sizes. We find that suspended particles substantially increase the anisotropy between the perpendicular and parallel friction coefficients acting on the beating flagellum, thereby enhancing propulsion. This effect is most pronounced when the suspended particles are comparable to or smaller than the characteristic wavelength of the flagellar beat. Experiments with microparticle suspensions confirm an increase in trypanosome propulsion with increasing particle concentration, in qualitative agreement with the simulations. Our results uncover a general physical mechanism by which concentrated particle suspensions can enhance flagellar-beat-driven locomotion and suggest that the densely crowded, particulate environment of blood may facilitate trypanosome propulsion. These findings provide new insight into trypanosome motility in the bloodstream and may apply broadly to other flagellated microswimmers in complex suspensions.

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Cite

BibTeX RIS

BibTeX

@misc{overberg2026trypanosome,
  title = {{Trypanosome motility in blood and particle suspensions}},
  author = {Florian A. Overberg and Marie Kater and Timothy Krüger and Gerhard Gompper and Markus Engstler and Dmitry A. Fedosov},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.02201},
  eprint = {2609.02201},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.02201},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - Trypanosome motility in blood and particle suspensions
AU  - Florian A. Overberg
AU  - Marie Kater
AU  - Timothy Krüger
AU  - Gerhard Gompper
AU  - Markus Engstler
AU  - Dmitry A. Fedosov
PY  - 2026
DA  - 2026/09/02
PB  - arXiv
DO  - 10.48550/arxiv.2609.02201
UR  - https://arxiv.org/abs/2609.02201
AB  - Motile microorganisms often navigate crowded and structurally complex environments, where surrounding obstacles can strongly influence locomotion. The bloodstream form of the flagellate parasite Trypanosoma brucei circulates in blood, a dense suspension of red blood cells (RBCs), yet the physical mechanisms governing its locomotion under such conditions remain poorly understood because direct experimental observations are challenging. Here, we combine numerical simulations with in vitro experiments to investigate trypanosome motility in concentrated RBC suspensions and in suspensions of spherical colloidal particles. Simulations reveal that the parasite swimming speed increases by up to 50% at RBC volume fractions comparable to those in blood. To identify the origin of this enhancement, we perform controlled studies in colloidal suspensions with particles of different sizes. We find that suspended particles substantially increase the anisotropy between the perpendicular and parallel friction coefficients acting on the beating flagellum, thereby enhancing propulsion. This effect is most pronounced when the suspended particles are comparable to or smaller than the characteristic wavelength of the flagellar beat. Experiments with microparticle suspensions confirm an increase in trypanosome propulsion with increasing particle concentration, in qualitative agreement with the simulations. Our results uncover a general physical mechanism by which concentrated particle suspensions can enhance flagellar-beat-driven locomotion and suggest that the densely crowded, particulate environment of blood may facilitate trypanosome propulsion. These findings provide new insight into trypanosome motility in the bloodstream and may apply broadly to other flagellated microswimmers in complex suspensions.
ER  -

Abstract

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