From solitary swimmers to swarms and back: trypanosomes on their journey through the tsetse fly

非洲锥虫在人类和牛中引起致命疾病。这种单细胞血液寄生虫寄生在哺乳动物宿主的体液中，也寄生在传播疾病的昆虫——臭名昭著的采采蝇的消化道中。锥虫是不间断的微游泳者，我们已经描述了它们在人体血液和组织空间中的运动行为。这个项目旨在了解游泳是如何促成寄生虫在苍蝇体内惊人的长途旅行的，这需要几个星期的时间。我们详细研究了采采蝇中八个不同锥虫生命周期阶段的细胞结构和游泳表现，并发现了显著不同的行为。虽然一些锥虫形式是单独游泳的，实际上显示出自我回避，但其他锥虫形成大群体，并表现出明显的集体行为。一些锥虫阶段沿着壁面游动，并在采采肠的奇异几何形状中导航。我们测量了采采蝇肠道的微环境，并利用基因工程和先进的成像方法，包括光片荧光显微镜，追踪了活蝇体内的锥虫。我们现在想挑战我们的发现，通过构建真正的受自然启发的微流体设备，密切模仿采采蝇体内的生物物理环境，包括限制、流动和粘度。有了这个，我们想要揭示不同阶段的锥虫在近水面游泳的独特能力，以及在禁闭中（集体）运动。高分辨率的数据将通过数值模拟和计算机模拟来解释，并将为鞭毛虫微游泳者的低雷诺数世界提供新的见解。

African trypanosomes cause deadly disease in human and cattle. The unicellular blood parasites populate the body fluids of their mammalian hosts, as well as the digestive tract of the disease transmitting insect, the infamous tsetse fly. Trypanosomes are incessant microswimmers, and we have characterized their motion behaviour in human blood and tissue spaces. This project aims at understanding how swimming contributes to the surprisingly long journey of the parasites through the fly, which takes several weeks. We have detailed the cell architectures and swimming performances of eight distinct trypanosome life cycle stages in the tsetse fly and found remarkably different behaviours. While some trypanosome forms are solitary swimmers and actually reveal self-avoidance, others form large swarms and show marked collective behaviour. Some trypanosome stages swim along walls and navigate within the bizarre geometries of the tsetse gut. We have measured the microenvironments the tsetse fly gut and have traced the trypanosomes in living flies using genetic engineering and advanced imaging methods, including light sheet fluorescence microscopy. We now want to challenge our findings by constructing true nature-inspired microfluidics devices that closely mimic the biophysical environments within the tsetse fly, including confinement, flows and viscosities. With this we want to unravel the distinct abilities of different trypanosome stages for near surface swimming, as well as (collective) motion in confinement. The high-resolution data will be interpreted by numerical modelling and computer simulations, and should provide new insights into the low Reynolds number world of flagellate microswimmers.