Real Time Chemotaxis in Commensal Plant-microbe Associations

植物与微生物、微生物与微生物之间的相互作用在根际发生，其结果影响植物的健康和生产力。细菌和宿主植物之间的分子通讯，允许建立特定的共生或致病植物-细菌相互作用是详细已知的。然而，在根际占主导地位的植物-微生物协会还没有被研究到相同的程度，相对较少的是已知的关于植物土壤细菌所使用的策略，以启动一个松散的协会与植物根表面或这些协会的时空动态。这项研究的目的是表征关键的细菌决定因素，涉及建立和维护的植物细菌协会和时空动态的这些协会，在实时。实验将表征巴西固氮菌与小麦根的关联中的传感和趋化作用，这是在高时空分辨率尺度上定量分析有益的植物-微生物关联的极好模型。使用实验和数学建模之间的迭代，该研究将表征多种趋化性途径提供给细菌感知和响应与其在土壤和根际生活方式相关的梯度的能力的选择优势。接下来，将确定能够整合代谢状态的受体在介导根际定殖中的作用。该项目还将使用一种新的表达系统来跟踪细胞内关键代谢物（c-di-GMP）浓度的变化如何影响真实的运动行为。最后，一个定量的方法来监测，在实时的传感和趋化性的作用，在时空动态的植物根定殖将实施。大多数土壤细菌与植物根形成共生关系，这些细菌的测序基因组编码至少两条Che途径。所获得的结果将直接转座到其他能动的土壤细菌，并将提供急需的定量见解的分子机制，参与建立植物-微生物协会。这方面的知识是一个先决条件，以系统水平的了解不同的植物微生物协会存在于根际。实时和定量监测植物-微生物协会的方法将首次记录这些协会的时空动态，并最终为未来有效的策略提供信息，以操纵根际，改善植物健康和生产力。更广泛的影响：该项目将提供新的工具和方法来定量分析植物-微生物协会的时空动态，包括实时跟踪根微生物协会的方法。从这项研究中得出的数学模型将是有用的，在未来的系统级模拟植物-微生物协会根际操纵和促进植物健康。该项目还将表征将增强合成生物学工具包的感觉模块。此外，将为研究生和本科生，包括科学领域代表性不足的群体的成员建立生物学和数学方面的跨学科互动。

Various plant-microbe and microbe-microbe interactions take place in the rhizosphere, the outcomes of which influence plant health and productivity. The molecular communication between bacteria and host plants that allow the establishment of specific symbiotic or pathogenic plant-bacteria interactions are known in detail. However, commensal plant-microbe associations that dominate in the rhizosphere have not been studied to the same extent and relatively little is known regarding the strategies used by commensal soil bacteria to initiate a loose association with plant root surfaces or the spatiotemporal dynamics of these associations. This research aims to characterize key bacterial determinants implicated in the establishment and maintenance of commensal bacteria-plant associations and the spatiotemporal dynamics of these associations, in real-time. Experiments will characterize the role of sensing and chemotaxis in the association of Azospirillum brasilense with wheat roots, which is an excellent model to quantitatively analyze beneficial commensal plant-microbe associations at high temporal and spatial resolution scales. Using iterations between experiments and mathematical modeling, the research will characterize the selective advantage that multiple chemotaxis pathways provide to the ability of bacteria to sense and respond to gradients relevant to their lifestyle in the soil and in the rhizosphere. Next, the role of receptors capable of integrating metabolic status with sensing in mediating rhizosphere colonization will be determined. The project will also use a novel expression system to track how changes in the intracellular concentration of a key metabolite (c-di-GMP) affect locomotor behaviors in real time. Last, a quantitative approach to monitor, in real-time, the role of sensing and chemotaxis in the spatiotemporal dynamics of commensal plant-root colonization will be implemented. Most soil bacteria form commensal associations with the roots of plants and the sequenced genomes of these bacteria encode at least two Che pathways. Results obtained will be directly transposable to other motile soil bacteria and will provide much needed quantitative insights into the molecular mechanisms involved in the establishment of commensal plant-microbe associations. This knowledge is a prerequisite to a systems-level understanding of the diverse plant-microbe associations that exist in the rhizosphere. The approach to real-time and quantitative monitoring of commensal plant-microbe associations will document the spatiotemporal dynamics of these associations for the first time and ultimately inform future effective strategies to manipulate the rhizosphere to improve plant health and productivity. Broader Impacts: This project will provide new tools and methods to quantitatively analyze the spatiotemporal dynamics of plant-microbe associations, including approaches to track real-time root-microbe associations. The mathematical model derived from this research will be useful in future systems-level simulations of plant-microbe associations for rhizosphere manipulation and promotion of plant health. The project will also characterize sensory modules that will enhance the synthetic biology toolkit. In addition, cross-disciplinary interactions in biology and mathematics for graduate students and undergraduate students, including members of underrepresented groups in the sciences, will be established.