随机性与环境切换塑造细菌群体中的群体感应进化

中文摘要 AI 辅助

群体感应（QS）经典上被理解为细菌细胞感知自身密度的机制，但环境波动使得任何单个细胞的估计都不可靠。另一种观点认为，群体汇集个体估计以达到可靠的集体决策。我们研究了双自诱导物拨动开关网络如何在波动环境中实现这种集体适应。在单细胞水平上，拨动开关是双稳态的。膜通透性控制自诱导物的分泌，并且是进化的性状。使用空间结构化种群的基于个体的模型，我们表明通透性通过集体机制进化。环境频率是进化结果的主要决定因素。在强不对称下，主导性状达到高平台。与稀有环境相关的性状保持低位。随着其环境变得更频繁，它平滑上升。总通透性保持接近固定预算；环境频率主要决定它如何在两个性状之间分配。当两个环境同样频繁时，没有单一性状获胜。两个性状共存，并且两个感知通道之间的噪声不对称性偏向它们共存的水平，而不是选择获胜者。共存也是达到的最慢结果。更高的噪声加速适应，但进化的通透性在噪声中是非单调的，在中间值达到峰值。早期工作发现，只要细胞平均正确，更多的噪声有利于集体感知。我们开发了一个双性状自适应动力学模型，统一了这些机制。远离对称性，它简化为一个封闭的一维方程，捕获了基于个体的结果。在对称性下，弱的交叉抑制给出一个单一的共存吸引子，与重复种群维持两个性状一致。

英文摘要

Quorum sensing (QS) is classically understood as a mechanism by which bacterial cells sense their own density, but environmental fluctuations make any single cell's estimate unreliable. An alternative view holds that populations pool individual estimates to reach reliable collective decisions. We investigate how a two-autoinducer toggle switch network enables this collective adaptation in fluctuating environments. At the single-cell level, the toggle switch is bistable. Membrane permeability controls autoinducer secretion and is the evolving trait. Using an individual-based model of a spatially structured population, we show that permeability evolves through a collective mechanism. Environmental frequency is the primary determinant of evolutionary outcome. Under strong asymmetry, the dominant trait reaches a high plateau. The trait linked to the rare environment stays low. It rises smoothly as its environment becomes more frequent. Total permeability stays close to a fixed budget; environmental frequency mainly sets how it is split between the two traits. When the two environments are equally frequent, no single trait wins. Both traits coexist, and noise asymmetry between the two sensing channels biases the levels at which they coexist rather than selecting a winner. Coexistence is also the slowest outcome to reach. Higher noise speeds adaptation, but the evolved permeability is non-monotonic in noise, peaking at an intermediate value. Earlier work found that more noise favors collective sensing as long as cells are correct on average. We develop a two-trait adaptive-dynamics model that unifies these regimes. Away from symmetry, it reduces to a closed one-dimensional equation that captures the individual-based results. At symmetry, weak cross-repression gives a single coexistence attractor, consistent with replicate populations maintaining both traits.

发表机构

• Academia Sinica（中央研究院）
• National Center for Theoretical Sciences（国家理论科学研究中心）

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