在其关于布朗运动的研究中，爱因斯坦意识到，处于静止状态的一种物质的随机分子运动也会影响到其他东西，比如说影响到它对于一个在外力作用下而穿过自己的粒子的阻力。这个现象后来被总结为“波动-响应定律”，但它是否适用于活细胞（活细胞的运动是远离平衡态的）仍然是一个尚未回答的问题。Park等人利用在细菌趋化现象研究中有可能实现的小尺度测量发现，“波动-响应定律”的确适用于单个细胞中细胞行为的时间波动（噪音）与细胞对外界的响应之间的关系。他们提出了确定生化网络中哪些特征使其内部状态与其对外部刺激的响应耦合在一起的方式。（生物谷Bioon.com）
生物谷推荐原文出处：
Nature doi:10.1038/nature09551
Interdependence of behavioural variability and response to small stimuli in bacteria
Heungwon Park,William Pontius,Calin C. Guet,John F. Marko,Thierry Emonet& Philippe Cluzel
The chemotaxis signalling network in Escherichia coli that controls the locomotion of bacteria is a classic model system for signal transduction1, 2. This pathway modulates the behaviour of flagellar motors to propel bacteria towards sources of chemical attractants. Although this system relaxes to a steady state in response to environmental changes, the signalling events within the chemotaxis network are noisy and cause large temporal variations of the motor behaviour even in the absence of stimulus3. That the same signalling network governs both behavioural variability and cellular response raises the question of whether these two traits are independent. Here, we experimentally establish a fluctuation–response relationship in the chemotaxis system of living bacteria. Using this relationship, we demonstrate the possibility of inferring the cellular response from the behavioural variability measured before stimulus. In monitoring the pre- and post-stimulus switching behaviour of individual bacterial motors, we found that variability scales linearly with the response time for different functioning states of the cell. This study highlights that the fundamental relationship between fluctuation and response is not constrained to physical systems at thermodynamic equilibrium4 but is extensible to living cells5. Such a relationship not only implies that behavioural variability and cellular response can be coupled traits, but it also provides a general framework within which we can examine how the selection of a network design shapes this interdependence
