发表机构
Institute for Advanced Simulation, Forschungszentrum Jülich; Julius-Maximilians-Universität of Würzburg（于利希研究中心先进模拟研究所; 维尔茨堡朱利叶斯-马克西米利安大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究结合数值模拟与体外实验，揭示高浓度颗粒悬浮液可通过增大鞭毛摩擦各向异性增强锥虫推进力，为理解锥虫血流运动及其他微游泳生物运动提供了新机制。
AI 中文摘要
能动微生物常需在拥挤且结构复杂的环境中运动，周围障碍物会强烈影响其运动。鞭毛寄生虫布氏锥虫的血流型在血液（红细胞（RBC）的致密悬浮液）中循环，然而由于直接实验观测颇具挑战性，其在该条件下运动的物理机制仍知之甚少。本研究结合数值模拟与体外实验，探究锥虫在高浓度RBC悬浮液及球形胶体颗粒悬浮液中的运动性。模拟显示，在与血液中RBC体积分数相当的情况下，寄生虫的游动速度可提升高达50%。为明确该增强效应的起源，研究人员在含不同尺寸颗粒的胶体悬浮液中开展受控研究，发现悬浮颗粒会显著增大作用于摆动鞭毛的垂直与平行摩擦系数间的各向异性，进而增强推进力；当悬浮颗粒尺寸与鞭毛摆动的特征波长相当或更小时，该效应最为显著。针对微颗粒悬浮液的实验证实，锥虫的推进力随颗粒浓度升高而增大，与模拟结果定性吻合。本研究揭示了一种通用物理机制：高浓度颗粒悬浮液可增强鞭毛摆动驱动的运动，并提示血液的致密颗粒环境或可促进锥虫推进；这些发现为锥虫在血流中的运动性提供了新见解，且可能广泛适用于复杂悬浮液中的其他带鞭毛微游泳生物。
英文摘要
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.
Comments13 pages, 5 figures
