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。智力优势生物使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。微生物具有两个组分的信号转导系统，它们调节细胞的许多行为，以应对环境的变化。这些行为之一是由趋化信号转导通路(CHE1)介导的定向运动。在模式微生物中，指导细菌在趋化过程中游泳模式的分子机制已经得到了详细的表征，并集中在鞭毛介导的定向运动上。巴西固氮螺菌在土壤中的趋化性涉及定向运动，但也与细胞长度的变化和细胞形成聚集体的趋势相协调。单细胞生物体形态的这些变化可能代表了对不断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。本项目致力于建立巴西乳杆菌趋化途径(CHE1)介导的趋化、聚集和细胞长度协调控制的分子基础。这项研究将在分子细节上表征细胞表面性质在聚集过程中的变化(目标1)。该项目将表征聚集细胞产生的低聚糖的结构，以及它们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识别负责细胞间相互作用的基因。该项目还将测试以下假设：反应调节器(CHEY)与极鞭毛马达复合体的相互作用通过对其他分子靶标的影响而导致细胞长度变化和聚集(研究目标2)。识别将感觉信息传递给Che1的化学受体的子集将通过开发一种新的实验方法来实现，将遗传上不相连的化学受体分配到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所使用的策略。这项研究将揭示趋化信号转导途径如何调节多种细胞反应，这将加深对细菌用来适应环境的复杂信号转导的理解。细菌中的广泛影响感知和行为独特地适合于拓宽大学生的教育经验，并使K-12学生能够开发基于研究的教育材料。本科生，包括那些来自科学界代表性不足的群体的学生，将参与正在进行的研究活动的各个方面，并为之做出贡献。这些学生将从田纳西大学现有的几个项目中招募。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的科学教师合作，通过开发和实施与科学课程相一致的适当动手练习，将研究传播到K6-12级别的课堂。制定的活动将通过在文理学院宣传网站上张贴向其他理科教师提供，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.