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In recent work, Engstler et al. showed that the motility of the trypanosomes, causative agents of African sleeping sickness, is essential in their evasion of the host immune response. Our studies reveal that the trypanosome travels in one of three distinct motility modes: random walk, directional persistence, and an intermediate class in which they exhibit a combination of both. To further elucidate the parasite's motility we utilize high-speed videomicroscopy to uncover the microscopic origin of the macroscopic motility modes. Trypanosome swimming is facilitated by a flagellum that runs along the cell body with only a small ‘free’ segment at the anterior end of the cell. We use a straightforward parameter, namely the distance between the anterior and posterior ends of the cell to characterize trypanosome swimming. Remarkably this parameter is sufficient for extraction of relevant time scales for classification of the motility modes. Further, we find not only that these different motility modes correspond to distinct physical movements but also that a stiffer cell body gives rise to directional persistence.Figure 1a) schematic of cell body b) typical swimming trajectories c) directionally persistent cells are ‘stretched’View Large Image | View Hi-Res Image | Download PowerPoint Slide |
