Chemotaxis And The Regulation Of Multiple Cellular Functions In A Bacterium

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。生物利用信号转导途径来感知和处理来自环境的信息。细胞对信息的反应对所有生物体的生存和生长至关重要。微生物具有双组分信号转导系统，它调节许多细胞行为以响应周围环境的变化。其中一种行为是由趋化性信号转导途径（Che1）介导的定向运动。在趋化过程中，指导细菌游动模式的分子机制已经在模式微生物中得到了详细的表征，并集中在鞭毛介导的定向运动上。土壤细菌氮螺旋菌的趋化性包括定向运动，但也与细胞长度的变化和细胞形成聚集体的倾向相协调。单细胞生物形态上的这些变化可能代表了对变化的环境条件的最简单的反应。然而，控制细菌运动和细胞形态的确切分子机制尚不清楚。本项目旨在建立巴西芽孢杆菌趋化途径（chemotactic pathway, Che1）介导的趋化性、聚集性和细胞长度协同调控的分子基础。该研究将详细描述细胞表面特性在聚集过程中的分子变化（目标1）。该项目将描述由聚集细胞特异性产生的低聚糖的结构及其与外膜蛋白的相互作用。全基因组微阵列和诱变实验将用于鉴定负责细胞间相互作用的基因。该项目还将测试反应调节因子（CheY）与极性鞭毛运动复合物的相互作用通过对其他分子靶标的影响导致细胞长度变化和聚集的假设（研究目标2）。将感觉信息传递给Che1的化学受体亚群的鉴定将通过开发一种新的实验方法来进行，该方法将遗传上不相关的化学受体分配到Che1途径（研究目标3）。这项研究的结果有望揭示细菌将感觉信息整合到细胞反应的协调框架中的策略。该研究将揭示趋化性信号转导途径如何调节多种细胞反应，这将改善对细菌适应环境所使用的复杂信号转导的理解。细菌中更广泛的影响感知和行为是唯一适合拓宽大学生的教育经验和使K-12学生的研究为基础的教育材料的发展。本科生，包括那些在科学领域代表性不足的群体，将参与并为正在进行的研究活动的各个方面做出贡献。这些学生将从田纳西大学现有的几个项目中招募。其中包括旨在促进科学教育的外联活动。特别是，本科生和研究生将与初中和高中科学教师合作，通过开发和实施与科学课程相一致的适当实践练习，将研究成果传播到K6-12年级的教室。制定的活动将通过发布在文理学院外联网站上提供给其他科学教师，这将扩大这些活动的影响。

This award is funded under the American Recovery and Reinvestment Act of 2009(Public Law 111-5).Intellectual Merit Organisms use signal transduction pathways to sense and process information from the environment. Cellular response to the information is critical to the survival and growth of all organisms. Microorganisms possess two-component signal transduction systems, which regulate numerous cellular behaviors in response to changes in the surroundings. One of these behaviors is directed movement mediated by a chemotaxis signal transduction pathway (Che1). Molecular mechanisms that direct the swimming pattern of bacteria during chemotaxis have been characterized in detail in model microorganisms, and have focused on flagellar mediated directed motility. Chemotaxis in the soil bacterium Azospirillum brasilense involves directional movement but also is coordinated with changes in cell length and the tendency of cells to form aggregates. These changes in the morphology of a unicellular organism may represent the simplest response to shifting environmental conditions. However, the exact molecular mechanisms controlling motility and cell morphology in bacteria are not known. This project focuses on establishing the molecular basis of the coordinated control of chemotaxis, aggregation, and cell length mediated by the chemotactic pathway (Che1) in A. brasilense. The research will characterize in molecular detail changes in cell surface properties during aggregation (objective 1). The project will characterize the structure of the oligosaccharides specifically produced by aggregating cells and their interaction with outer membrane proteins. Whole-genome microarray and mutagenesis experiments will be used to identify the genes responsible for cell-to-cell interactions. The project will also test the hypothesis that interaction of the response regulator (CheY) with the polar flagellar motor complex results in cell length changes and aggregation via an effect on other molecular target(s) (research objective 2). The identification of the subset of chemoreceptors that relay sensory information to Che1 will be carried out by developing a novel experimental approach to assign genetically unlinked chemoreceptors to the Che1 pathway (research objective 3). Results from this research are expected to shed light into the strategies used by bacteria to integrate sensory information into a coordinated framework of cellular responses. The research will reveal how a chemotaxis signal transduction pathway modulates multiple cellular responses which will refine understanding of complex signal transduction used by bacteria to adapt to the environment.Broader Impact Sensing and behavior in bacteria are uniquely suited for broadening the educational experiences of college students and enabling the development of research-based educational materials for K-12 students. Undergraduate students, including those from underrepresented groups in the sciences, will participate and contribute to all aspects of the on-going research activities. These students will be recruited from several existing programs at the University of Tennessee. Outreach activities aimed at promoting science education are included. In particular, undergraduate and graduate students will be partnered with middle and high school science teachers to disseminate research to K6-12 level classrooms by developing and implementing appropriate hands-on exercises that align with the science curriculum. The activities developed will be made available to other science teachers by posting on the College of Arts and Sciences outreach website, which will broaden the impact of these activities.