Day Thomas C, Zamani-Dahaj S Alireza, Bozdag G Ozan, Burnetti Anthony J, Bingham Emma P, Conlin Peter L, Ratcliff William C, Yunker Peter J
School of Physics, Georgia Institute of Technology.
School of Biological Sciences, Georgia Institute of Technology.
Phys Rev X. 2024 Jan-Mar;14(1). doi: 10.1103/physrevx.14.011008. Epub 2024 Jan 25.
Many organisms exhibit branching morphologies that twist around each other and become entangled. Entanglement occurs when different objects interlock with each other, creating complex and often irreversible configurations. This physical phenomenon is well studied in nonliving materials, such as granular matter, polymers, and wires, where it has been shown that entanglement is highly sensitive to the geometry of the component parts. However, entanglement is not yet well understood in living systems, despite its presence in many organisms. In fact, recent work has shown that entanglement can evolve rapidly and play a crucial role in the evolution of tough, macroscopic multicellular groups. Here, through a combination of experiments, simulations, and numerical analyses, we show that growth generically facilitates entanglement for a broad range of geometries. We find that experimentally grown entangled branches can be difficult or even impossible to disassemble through translation and rotation of rigid components, suggesting that there are many configurations of branches that growth can access that agitation cannot. We use simulations to show that branching trees readily grow into entangled configurations. In contrast to nongrowing entangled materials, these trees entangle for a broad range of branch geometries. We, thus, propose that entanglement via growth is largely insensitive to the geometry of branched trees but, instead, depends sensitively on timescales, ultimately achieving an entangled state once sufficient growth has occurred. We test this hypothesis in experiments with snowflake yeast, a model system of undifferentiated, branched multicellularity, showing that lengthening the time of growth leads to entanglement and that entanglement via growth can occur for a wide range of geometries. Taken together, our work demonstrates that entanglement is more readily achieved in living systems than in their nonliving counterparts, providing a widely accessible and powerful mechanism for the evolution of novel biological material properties.
许多生物体呈现出相互缠绕并纠缠在一起的分支形态。当不同物体相互联锁时就会发生纠缠，从而形成复杂且往往不可逆的构型。这种物理现象在非生物材料中得到了充分研究，如颗粒物质、聚合物和金属丝，研究表明纠缠对组成部分的几何形状高度敏感。然而，尽管许多生物体中都存在纠缠现象，但在生命系统中人们对其仍未完全理解。事实上，最近的研究表明，纠缠可以迅速演化，并在坚韧的宏观多细胞群体的演化中发挥关键作用。在这里，通过实验、模拟和数值分析相结合的方法，我们表明，对于广泛的几何形状，生长通常会促进纠缠。我们发现，通过实验生长的纠缠分支很难甚至不可能通过刚性组件的平移和旋转来拆解，这表明存在许多生长能够达到但搅动无法达到的分支构型。我们用模拟表明，分支树很容易生长成纠缠构型。与不生长的纠缠材料不同，这些树在广泛的分支几何形状下都会发生纠缠。因此，我们提出，通过生长产生的纠缠在很大程度上对分支树的几何形状不敏感，而是敏感地取决于时间尺度，一旦发生足够的生长，最终会达到纠缠状态。我们在雪花酵母（一种未分化的分支多细胞模型系统）的实验中检验了这一假设，结果表明延长生长时间会导致纠缠，并且对于广泛的几何形状都能通过生长产生纠缠。综上所述，我们的工作表明，在生命系统中比在非生命系统中更容易实现纠缠，这为新型生物材料特性的演化提供了一种广泛适用且强大的机制。
