Bacteria have the ability to directly sense their environment and change their behavior according to their surroundings. While the behavioral changes in the bacteria can be seen visually, the intricate genetic processes that lead to some of the changes are not fully understood. This project will investigate some of the ways in which bacteria carry out these processes using Sinorhizobium meliloti as a model. Sinorhizobium meliloti is a member of a larger group of bacteria called rhizobia, and is environmentally and economically vital in the field of agriculture. Sinorhizobium beneficially infects legumes and provides useable nitrogen to increase crop yield. An efficient and productive rhizobium infection reduces the need for chemical fertilizers. Expanding our knowledge of the genetic systems that control the behavior of this bacterium has the potential to allow manipulation to optimize the rhizobium-plant interaction. The project will train students from the across educational levels, from high school to graduate students to do scientific work in this field and to communicate it properly. <br/><br/>The overarching goal of this proposal is to investigate and understand the role of a hybrid phosphotransferase system (PTS) and a unique two component signal transduction system in regulating gene expression in the bacterial nitrogen-fixing gram-negative symbiont Sinorhizobium meliloti. The project will study a recently identified and novel interaction between the two systems that regulates several cellular processes. Additionally, the systems themselves are interesting and insufficiently characterized: the phosphotransferase system is an abbreviated nitrogen-sugar hybrid while the two-component system has an intriguing multiple-sensing domain HWE kinase (Sma0113) and an atypical response regulator with no effector domain (Sma0114). One of the processes under dual regulation is catabolite repression. This is a complex process through which bacterial cells adapt to obtain energy and raw materials, and, in related bacteria, controls the expression of genes associated to their ability to interact with their hosts. Three approaches will be used to elucidate how the systems are integrated into the cellular network. Transcriptome analysis will allow identification of the combined regulon of the two systems. Genetic, biochemical, and proteomic methods will reveal their downstream partners. Genetic tools will be used to characterize the promoter structure that allows dual regulation. The results will bring better understanding of the characteristics of the two systems and the role each plays in regulating gene expression in S. meliloti and similar gram negative bacteria.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.