Department of Electrical and Computer Engineering, 94 Brett Road, Rutgers, The State University of New Jersey, Piscataway, NJ 08854-8058, USA.
J R Soc Interface. 2013 Jan 4;10(80):20120935. doi: 10.1098/rsif.2012.0935. Print 2013 Mar 6.
The chemotaxis pathway of the bacterium Rhodobacter sphaeroides shares many similarities with that of Escherichia coli. It exhibits robust adaptation and has several homologues of the latter's chemotaxis proteins. Recent theoretical results have correctly predicted that the E. coli output behaviour is unchanged under scaling of its ligand input signal; this property is known as fold-change detection (FCD). In the light of recent experimental results suggesting that R. sphaeroides may also show FCD, we present theoretical assumptions on the R. sphaeroides chemosensory dynamics that can be shown to yield FCD behaviour. Furthermore, it is shown that these assumptions make FCD a property of this system that is robust to structural and parametric variations in the chemotaxis pathway, in agreement with experimental results. We construct and examine models of the full chemotaxis pathway that satisfy these assumptions and reproduce experimental time-series data from earlier studies. We then propose experiments in which models satisfying our theoretical assumptions predict robust FCD behaviour where earlier models do not. In this way, we illustrate how transient dynamic phenotypes such as FCD can be used for the purposes of discriminating between models that reproduce the same experimental time-series data.
球形红杆菌的趋化途径与大肠杆菌的趋化途径有许多相似之处。它表现出强大的适应性，并且有几个与后者趋化蛋白同源的蛋白。最近的理论结果正确地预测了大肠杆菌的输出行为在其配体输入信号的缩放下保持不变；这种特性被称为倍数变化检测（FCD）。鉴于最近的实验结果表明，球形红杆菌也可能表现出 FCD，我们提出了关于球形红杆菌化学感觉动力学的理论假设，这些假设可以产生 FCD 行为。此外，结果表明，这些假设使 FCD 成为该系统的一个特性，对趋化途径的结构和参数变化具有鲁棒性，与实验结果一致。我们构建并检查了满足这些假设的完整趋化途径模型，并再现了早期研究中的实验时间序列数据。然后，我们提出了一些实验，其中满足我们理论假设的模型预测了在早期模型中没有的稳健的 FCD 行为。通过这种方式，我们说明了如何将 FCD 等瞬态动态表型用于区分再现相同实验时间序列数据的模型。
