Emergent programmable behavior and chaos in dynamically driven active filaments

How the behavior of cells emerges from their constituent subcellular biochemical and physical parts is an outstanding challenge at the intersection of biology and physics. A remarkable example of single-cell behavior occurs in the ciliate Lacrymaria olor, which hunts for its prey via rapid movements and protrusions of a slender neck, many times the size of the original cell body. The dynamics of this cell neck is powered by a coat of cilia across its length and tip. How a cell can program this active filamentous structure to produce desirable behaviors like search and homing to a target remains unknown. Here, we present an active filament model that allows us to uncover how a “program” (time sequence of active forcing) leads to “behavior” (filament shape dynamics). Our model captures two key features of this system—time-varying activity patterns (extension and compression cycles) and active stresses that are uniquely aligned with the filament geometry—a “follower force” constraint. We s...细胞行为如何由其组成的亚细胞生化与物理组分涌现而来，是生物学与物理学交叉领域中的一项重大未解挑战。单细胞行为的典型范例来自尖鼻虫（Lacrymaria olor）：它通过细长颈部的快速运动与伸出动作捕猎猎物，该颈部长度可达细胞本体的数倍。该细胞颈部的运动由覆盖其全长与尖端的纤毛（cilia）驱动。细胞如何调控这一活性丝状结构，以实现搜索、靶向归巢等理想行为，目前仍未可知。本研究提出一种活性丝状模型，用以揭示"调控程序"（活性驱动的时间序列）如何催生"行为表现"（丝状结构的形状动力学）。该模型捕捉了该系统的两项核心特征：时变活性模式（伸展与压缩循环），以及与丝状几何结构唯一匹配的活性应力——即"跟随力"约束。我们的