Alim Karen, Andrew Natalie, Pringle Anne, Brenner Michael P
The Kavli Institute for Bionano Science and Technology, Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138;
Max Planck Institute for Dynamics and Self-Organization, 37077 Goettingen, Germany.
Proc Natl Acad Sci U S A. 2017 May 16;114(20):5136-5141. doi: 10.1073/pnas.1618114114. Epub 2017 May 2.
Complex behaviors are typically associated with animals, but the capacity to integrate information and function as a coordinated individual is also a ubiquitous but poorly understood feature of organisms such as slime molds and fungi. Plasmodial slime molds grow as networks and use flexible, undifferentiated body plans to forage for food. How an individual communicates across its network remains a puzzle, but has emerged as a novel model used to explore emergent dynamics. Within , cytoplasm is shuttled in a peristaltic wave driven by cross-sectional contractions of tubes. We first track 's response to a localized nutrient stimulus and observe a front of increased contraction. The front propagates with a velocity comparable to the flow-driven dispersion of particles. We build a mathematical model based on these data and in the aggregate experiments and model identify the mechanism of signal propagation across a body: The nutrient stimulus triggers the release of a signaling molecule. The molecule is advected by fluid flows but simultaneously hijacks flow generation by causing local increases in contraction amplitude as it travels. The molecule is initiating a feedback loop to enable its own movement. This mechanism explains previously puzzling phenomena, including the adaptation of the peristaltic wave to organism size and 's ability to find the shortest route between food sources. A simple feedback seems to give rise to 's complex behaviors, and the same mechanism is likely to function in the thousands of additional species with similar behaviors.
复杂行为通常与动物相关联，但整合信息并作为一个协调个体发挥功能的能力，也是黏菌和真菌等生物体普遍存在但却知之甚少的特征。多核变形虫状黏菌以网络形式生长，并利用灵活、未分化的身体结构觅食。个体如何在其网络中进行通信仍是一个谜题，但它已成为用于探索涌现动力学的一种新模型。在其内部，细胞质在由管道横截面收缩驱动的蠕动波中穿梭。我们首先追踪其对局部营养刺激的反应，并观察到收缩增加的前沿。该前沿的传播速度与颗粒的流动驱动扩散速度相当。我们基于这些数据构建了一个数学模型，并在总体实验和模型中确定了信号在整个生物体中传播的机制：营养刺激触发信号分子的释放。该分子由流体流动平流输送，但在其传播过程中，会通过引起局部收缩幅度增加，同时劫持流动的产生。该分子正在启动一个反馈回路以实现自身的移动。这种机制解释了以前令人困惑的现象，包括蠕动波对生物体大小的适应性以及其找到食物源之间最短路径的能力。一种简单的反馈似乎产生了其复杂行为，并且相同的机制可能在数千种具有类似行为的其他物种中发挥作用。
