Chemotactic Response and Adaptation Dynamics in Escherichia coli
Chemotactic Response and Adaptation Dynamics in Escherichia coli
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DOI：
10.1371/journal.pcbi.1000784
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发表时间：
2010-05-01
影响因子：
4.3
通讯作者：
Endres, Robert G.
中科院分区：
文献类型：
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作者：
Clausznitzer, Diana;Oleksiuk, Olga;Endres, Robert G.
大肠杆菌趋化性感觉通路的适应对于在广泛的背景浓度范围内检测化学物质是必不可少的，最终允许细胞游向引诱剂的来源而远离驱避剂。其以化学感受器甲基化和去甲基化为基础的生化机制早已为人所知。尽管适应对细胞记忆和行为很重要，但适应的动态很难与目前的精确适应模型相协调。在这里，我们使用体内荧光共振能量转移测量来跟踪信号对引诱剂浓度阶跃变化的响应的时间进程。具体地说，我们使用适应时间进程的浓缩表示来有效地评估不同的适应模型。为了定量地解释这些数据，我们最终建立了一个基于实验中的吸引剂流动、合作受体复合体的信号传递和适应的多层反馈调节的信号和适应的动态模型。我们在实验上证实了改变酶表达水平和绕过去甲基化的负反馈的预期效果。我们的数据分析表明，在适应大量增加方面存在显著的不精确性。此外，我们的模型预测了高度调节的、超快的适应响应于吸引剂的去除，这可能有助于细胞的快速重新定位和适应中的噪音降低。
Adaptation of the chemotaxis sensory pathway of the bacterium Escherichia coli is integral for detecting chemicals over a wide range of background concentrations, ultimately allowing cells to swim towards sources of attractant and away from repellents. Its biochemical mechanism based on methylation and demethylation of chemoreceptors has long been known. Despite the importance of adaptation for cell memory and behavior, the dynamics of adaptation are difficult to reconcile with current models of precise adaptation. Here, we follow time courses of signaling in response to concentration step changes of attractant using in vivo fluorescence resonance energy transfer measurements. Specifically, we use a condensed representation of adaptation time courses for efficient evaluation of different adaptation models. To quantitatively explain the data, we finally develop a dynamic model for signaling and adaptation based on the attractant flow in the experiment, signaling by cooperative receptor complexes, and multiple layers of feedback regulation for adaptation. We experimentally confirm the predicted effects of changing the enzyme-expression level and bypassing the negative feedback for demethylation. Our data analysis suggests significant imprecision in adaptation for large additions. Furthermore, our model predicts highly regulated, ultrafast adaptation in response to removal of attractant, which may be useful for fast reorientation of the cell and noise reduction in adaptation.