Spatial Information, Information Flows, and Dissipation in Models for Migration Waves of Chemotactic Bacterial Populations.

许多生物物种形成群体是为了增加生存的机会。这些群体通常依靠个体之间的交流来维持其结构。在这些情况下，每个个体都需要通过提供信息来投资于群体，但从它可以提取的信息中获得利益。该项目将通过使用趋化细菌种群的迁移波作为模型来量化控制这种信息交换的基本规则。这些细菌追逐一种化学梯度，这种梯度是由它们的集体消耗产生的。该系统中的相互作用是由环境化学成分的空间结构介导的。单个细菌通过消耗或分泌化学物质在局部产生信息，它们通过检测群体产生的化学场的随时间变化和梯度来提取信息。因此，环境调解了一种间接的通信交换。我将分三个阶段对这一过程进行建模：首先，我将应用非平衡态热力学的最新思想来解释个体在其环境中留下的空间结构中包含的信息，以及这样做所需的工作。其次，我将把信息流的测量从信息论扩展到细胞尺度，以量化一个感知细胞可以接收到多少关于其环境中空间结构的信息。最后，我将结合这些见解来模拟形成迁移浪潮的趋化细菌群体中的信息交换过程。有了这个理论模型，我将能够量化信息是如何在这个系统中流动的，需要多少能量来维持波的结构，有多少能量被消耗，以及这个过程的效率。我还将能够评估细菌种群的多样性在多大程度上对维持群体结构有益或有害。

Many biological species form groups in order to increase chances of survival. These groups often rely on communication between individuals to retain their structure. In these cases, each individual needs to invest into the group by providing information but gains benefits from the information it can extract. This project will quantify the fundamental rules governing this type of information exchange by using migration waves of chemotactic bacterial populations as a model. These are bacteria that chase a chemical gradient which is generated by their collective consumption.The interactions in this system are mediated by the spatial structure in the chemical composition of the environment. Individual bacteria generate information locally by consuming or secreting chemicals, and they extract information by detecting time-dependent changes and gradients in the chemical fields generated by the group. The environment thus mediates an indirect communication exchange.I will model this process in three stages: First, I will apply recent ideas from nonequilibrium thermodynamics to account for the information contained in the spatial structures that an individual imprints on its environment, and the work that is required to do so. Second, I will extend a measure of information flow from information theory to the cellular scale in order to quantify how much information a sensing cell can receive about spatial structures in its environment. Last, I will combine these insights to model the information exchange processes in a population of chemotactic bacteria that forms a migration wave.With this theoretical model I will be able to quantify how information is flowing through this system, how much energy is required to maintain the wave structure, how much energy is being dissipated, and how efficient this process is. I will furthermore be able to evaluate to which extent diversity in a bacterial population is beneficial or detrimental to maintaining the group's structure.