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.
