To complete its infectious cycle, the protozoan parasite Trypanosoma brucei must navigate through diverse tissue environments in both its tsetse fly and mammalian hosts. This is hypothesized to be driven by yet unidentified chemotactic cues. Prior work has shown that parasites engaging in social motility in vitro alter their trajectory to avoid other groups of parasites, an example of negative chemotaxis. However, movement of T. brucei toward a stimulus, positive chemotaxis, has so far not been reported. Here, we show that upon encountering Escherichia coli, socially behaving T. brucei parasites exhibit positive chemotaxis, redirecting group movement toward the neighboring bacterial colony. This response occurs at a distance from the bacteria and involves active changes in parasite motility. By developing a quantitative chemotaxis assay, we show that the attractant is a soluble, diffusible signal dependent on actively growing E. coli. Time-lapse and live video microscopy revealed that T. brucei chemotaxis involves changes in both group and single cell motility. Groups of parasites change direction of group movement and accelerate as they approach the source of attractant, and this correlates with increasingly constrained movement of individual cells within the group. Identification of positive chemotaxis in T. brucei opens new opportunities to study mechanisms of chemotaxis in these medically and economically important pathogens. This will lead to deeper insights into how these parasites interact with and navigate through their host environments.

中文翻译：

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原生动物病原体布氏锥虫中阳性趋化性的鉴定。

为了完成其传染周期，原生动物寄生虫布氏锥虫必须在其采采蝇和哺乳动物宿主的不同组织环境中导航。假设这是由尚未确定的趋化线索驱动的。先前的工作表明，参与体外社会运动的寄生虫会改变它们的轨迹，以避免其他寄生虫群体，这是负趋化性的一个例子。然而，迄今为止，尚未报道布氏木霉向刺激、正向趋化性的运动。在这里，我们表明，在遇到大肠杆菌时，具有社会行为的布氏布鲁氏菌寄生虫表现出积极的趋化性，将群体运动重新定向到邻近的细菌菌落。这种反应发生在远离细菌的地方，并涉及寄生虫运动的积极变化。通过开发定量趋化性测定，我们表明引诱剂是一种依赖于活跃生长的大肠杆菌的可溶性、可扩散信号。延时和实时视频显微镜显示布氏锥虫趋化性涉及组和单细胞运动的变化。成群的寄生虫在接近引诱剂来源时会改变群体运动的方向并加速，这与群体内单个细胞的运动越来越受限有关。布鲁氏菌阳性趋化性的鉴定为研究这些医学上和经济上重要的病原体的趋化机制开辟了新的机会。这将导致更深入地了解这些寄生虫如何与宿主环境相互作用并在其宿主环境中导航。