Thermally robust chemotaxis and thermotaxis in Escherichia coli

描述（由申请人提供）：在细菌环境中，温度变化和温度梯度与化学变化和梯度一样普遍存在。对于细菌来说，找到温度和营养的最佳组合对于最大限度地生长至关重要。事实上，细菌在大范围的温度下执行趋化性，并在温度梯度中执行定向运动，即执行趋热性。在大肠杆菌中，趋化性和趋热性都利用了相同的良好表征的信号网络。这项研究的具体目的是开发一个预测，定量的了解这个网络的热性能。将实验与建模相结合将有助于回答几个基本问题：什么样的网络特征允许在广泛的温度范围内具有强大的趋化性？信号网络如何同时允许趋化性和趋热性？多种感官刺激如引诱剂/驱避剂和温度变化如何相互作用？我们的初步结果表明，趋化途径的各个步骤是温度依赖性的，但在系统水平上，这些依赖性相互补偿。为了量化这些观测结果，我们将获得E.大肠杆菌趋化性信号通路使用单拴系细胞测量和多细胞FRET研究。我们帮助开发的现有趋化性理论将指导有效的数据采集，相同的理论将用作建模的基础。为明确E.大肠杆菌的趋热性，并扩展了我们已经建立的初步趋热性模型，E.大肠杆菌将通过拴系细胞和FRET研究进行系统测量。所有的实验研究将利用我们大量的预先存在的工程突变株的E。杆菌我们的研究结果可能对许多细胞信号网络具有重要意义。由于温度可能会影响所有信号通路的所有组分，因此我们的研究结果可能揭示细胞在一定温度范围内确保忠实信号的通用机制。此外，由于细菌的趋化性网络与感染性有关，并且在细菌中广泛存在且保守，但不为人类所共有，因此该途径为未来抗生素的开发提供了潜在的靶点。公共卫生相关性：这项研究的目的是更深入地了解允许细菌执行趋化性和趋热性的蛋白质网络，即分别感知和游向食物或偏好的温度。我们建议通过紧密耦合的实验方法和计算建模来发展这样的理解。从人类健康的角度来看，细菌病原体的趋化性与疾病的感染性和维持有关，趋热性也可能有关。由于趋化性/趋热性网络在细菌中分布广泛且保守，但不为人类所共享，因此该途径为未来抗生素的开发提供了潜在的靶点。此外，由于活细胞内的所有信号通路必须在波动的热环境中发挥作用，我们的努力可能揭示细胞确保忠实信号的普遍机制。

DESCRIPTION (provided by applicant): In the bacterial environment, temperature variation and temperature gradients are as ubiquitous as chemical variation and gradients. For bacteria, locating the optimal combination of temperature and nutrients is crucial for maximizing growth. Indeed, bacteria perform chemotaxis over a large range of temperatures and perform directed motion in temperature gradients, i.e. perform thermotaxis. In Escherichia coli, chemotaxis and thermotaxis both exploit the same well-characterized signaling network. The specific aim of this research is to develop a predictive, quantitative understanding of the thermal properties of this network. Combining experiment with modeling will help answer several fundamental questions: What network features allow robust chemotaxis over a wide range of temperatures? How does the signaling network allow both chemotaxis and thermotaxis? How do multiple sensory stimuli such as attractants/repellants and temperature changes interact? Our preliminary results indicate that the individual steps of the chemotaxis pathway are temperature dependent, but that at the systems level, these dependencies compensate for one another. To quantify these observations, we will obtain temperature-dependent data on the individual steps of the E. coli chemotactic signaling pathway using single-tethered-cell measurements and multi-cell FRET studies. The existing theory for chemotaxis that we have helped develop will guide efficient data acquisition, and the same theory will be used as the basis for modeling. To determine the molecular mechanism(s) underlying E. coli thermotaxis, and to extend a preliminary thermotaxis model we have developed, the thermotactic response of E. coli will be systematically measured via tethered-cell and FRET studies. All experimental studies will exploit our large pre-existing collection of engineered mutant strains of E. coli. Our results are likely to have significance for many cellular signaling networks. Because temperature potentially affects all components of all signaling pathways, our results may reveal universal mechanisms used by cells to ensure faithful signaling over a range of temperatures. Also, since the chemotaxis network of bacteria has been implicated in infectivity, and is widespread and well conserved among bacteria but is not shared by humans, the pathway presents a potential target for the development of future antibiotics. PUBLIC HEALTH RELEVANCE: The aim of this research is to develop a deeper understanding of the network of proteins that allows bacteria to perform chemotaxis and thermotaxis, that is to sense and swim towards food or a preferred temperature, respectively. We propose to develop such an understanding through closely coupled experimental approaches and computational modeling. From a human health perspective, chemotaxis by bacterial pathogens has been implicated in infectivity and maintenance of disease, and thermotaxis may be implicated as well. Since the chemotaxis/thermotaxis network is widespread and well conserved among bacteria, but is not shared by humans, the pathway presents a potential target for the development of future antibiotics. In addition, as all signaling pathways within living cells must function in the context of fluctuating thermal environments, our efforts may reveal universal mechanisms by which cells ensure faithful signaling.