Narayanasamy Nishant, Bingham Emma, Fadero Tanner, Bozdag G Ozan, Ratcliff William C, Yunker Peter, Thutupalli Shashi
Simons Centre for the Study of Living Machines, National Centre for Biological Sciences (TIFR), Bangalore, India.
School of Physics, Georgia Institute of Technology, Atlanta, GA, USA.
Sci Adv. 2025 Jun 20;11(25):eadr6399. doi: 10.1126/sciadv.adr6399.
The ecological and evolutionary success of multicellular lineages stems substantially from their increased size relative to unicellular ancestors. However, large size poses biophysical challenges, especially regarding nutrient transport: These constraints are typically overcome through multicellular innovations. Here, we show that an emergent biophysical mechanism-spontaneous fluid flows arising from metabolically generated density gradients-can alleviate constraints on nutrient transport, enabling exponential growth in nascent multicellular clusters of yeast lacking any multicellular adaptations for nutrient transport or fluid flow. Beyond a threshold size, the metabolic activity of experimentally evolved snowflake yeast clusters drives large-scale fluid flows that transport nutrients throughout the cluster at speeds comparable to those generated by ciliary actuation in extant multicellular organisms. These flows support exponential growth at macroscopic sizes that theory predicts should be diffusion limited. This demonstrates how simple physical mechanisms can act as a "biophysical scaffold" to support the evolution of multicellularity by opening up phenotypic possibilities before genetically encoded innovations.
多细胞谱系在生态和进化上的成功很大程度上源于其相对于单细胞祖先而言增大的体型。然而，较大的体型带来了生物物理挑战，尤其是在营养物质运输方面：这些限制通常通过多细胞创新得以克服。在此，我们表明一种新兴的生物物理机制——由代谢产生的密度梯度引发的自发流体流动——能够缓解营养物质运输的限制，使缺乏任何用于营养物质运输或流体流动的多细胞适应性的新生酵母多细胞簇实现指数增长。超过阈值大小后，实验进化出的雪花酵母簇的代谢活动驱动大规模流体流动，这些流动以与现存多细胞生物中纤毛驱动产生的速度相当的速度在整个簇中运输营养物质。这些流动支持了宏观尺寸下的指数增长，而理论预测这种尺寸下应该受扩散限制。这证明了简单的物理机制如何能够充当“生物物理支架”，通过在基因编码的创新之前开辟表型可能性来支持多细胞性的进化。
