趋化E. coli不计单分子
Chemotaxing E. coli do not count single molecules
AI总结：
研究发现E. coli趋化感知受限于内部噪声而非分子扩散物理限制，通过信息率分析显示其信息编码量远低于物理极限。
摘要：
生物体利用专门传感器测量环境，但决定其准确性的基本原理仍不明确。在大肠杆菌趋化中，我们先前发现梯度爬升速度受细胞从环境中获取信息量的限制，并且E. coli接近此极限。然而，仍不清楚为何它们无法获取更多信息。以往研究认为E. coli趋化感知受限于分子随机到达细胞受体的物理限制，但缺乏直接证据。本文显示E. coli远低于此物理极限。为此，我们开发了一种理论方法，利用信息率量化如何从可用观测中准确估计行为相关信号：分子到达用于物理极限；趋化信号活动用于E. coli。通过单细胞实验在多种背景浓度下测量这些信息率，发现E. coli编码的信息量比物理极限低两个数量级。因此，E. coli趋化感知受限于信号处理中的内部噪声，而非分子扩散的物理限制，推动了对塑造这一典型感觉系统进化特性的具体物理和生物约束的调查。
英文摘要：
Organisms use specialized sensors to measure their environments, but the fundamental principles that determine their accuracy remain largely unknown. In Escherichia coli chemotaxis, we previously found that gradient-climbing speed is bounded by the amount of information that cells acquire from their environment, and that E. coli operate near this bound. However, it remains unclear what prevents them from acquiring more information. Past work argued that E. coli's chemosensing is limited by the physics of molecules stochastically arriving at cells' receptors, without direct evidence. Here, we show instead that E. coli are far from this physical limit. To show this, we develop a theoretical approach that uses information rates to quantify how accurately behaviorally-relevant signals can be estimated from available observations: molecule arrivals for the physical limit; chemotaxis signaling activity for E. coli. Measuring these information rates in single-cell experiments across multiple background concentrations, we find that E. coli encode two orders of magnitude less information than the physical limit. Thus, E. coli chemosensing is limited by internal noise in signal processing rather than the physics of molecule diffusion, motivating investigation of what specific physical and biological constraints shaped the evolution of this prototypical sensory system.
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