English: Particle displacement by trypanosomes. Beads of varying size and mass were used to simulate different degrees of particle crowding and to estimate the force a trypanosome flagellum can exert on the environment. (A, B) At low particle density and without stirring Dynabeads cluster similar to blood cells. Note that both the tumbling cell as well as the directionally swimming trypanosome is able to efficiently displace the beads. (C) Trypanosomes move effectively even when covered with a dense layer of beads. The inset shows displacement of large polystyrene beads recorded by high-speed microscopy. The mass of this particular type of beads (density: 1,05 g/cm3) and the average distance of displacement (roughly 2 µm in 30 ms) points to a force of minimally 5 pN produced by a flagellar deflection. (D) Left video: Fluorescently labeled trypanosomes recorded in freshly drawn mouse blood. The blood cells are displaced but not deformed by the trypanosomes. Right video: Trypanosomes displace erythrocytes in a 40 µm microfluidic channel without any obvious deformation of the cells. This means that the effective force of the trypanosome flagellum must be significantly smaller than 100 pN.