Wednesday, January 15, 2025
1/15/2025
PROJECT SUMMARY Staphylococcus aureus is a gram-positive bacterium that colonizes the nares of ~30% of the human population and is the most common cause of bacteremia, endocarditis, and skin and soft tissue infections. Environmental nitrogen acquisition is essential for bacterial growth. To meet intracellular nitrogen requirements, S. aureus requires the transport of exogenous nitrogen via cytosolic NH4+ ions, amino acids, nitrate, nitrite, or urea. A common nitrogen source for many pathogens is glutamine, which along with glutamate function as the primary amino donors for cellular reactions requiring nitrogen. Since many precursor molecules for glutamine synthesis are also essential for other intracellular reactions, these pathways are tightly regulated processes affected by intracellular glutamine concentrations. Human hosts have a high level of free glutamine, so we hypothesized that glutamine transport serves as the primary route for nitrogen acquisition in S. aureus. However, glutamine transport alone does not cause a virulence defect in S. aureus. We therefore hypothesize that S. aureus uses preferred nitrogen sources and that intracellular glutamate and NH4+ pools are regulated by GltC and GlnR, respectively. This hypothesis will be addressed by two experimental aims. In aim 1, we will use 15N- isotopolog tracing experiments with LC-MS to identify preferred nitrogen sources in aerobic, microaerobic, and anaerobic conditions. Additionally, we will use both a bacteremia and skin soft tissue model of infection to determine if nitrogen limitation results in a physiological phenotype. In aim 2 we will use a gel-shift assay to characterize the DNA binding activity of the nitrogen metabolic regulator GlnR both individually and in the feedback inhibited glutamine synthetase (FBI-GS) complex with glutamine. We will also identify and evaluate the function of the regulatory GltC using qRT-PCR and RNAseq. This project seeks to research the unexplored role of nitrogen metabolism and regulation in S. aureus pathogenesis. Additionally, these data will inform systems biology approaches to determine novel therapeutic approaches to inhibit staphylococcal disease. The knowledge and training that I will gain through the experiments and activities proposed in this F30 application will provide me a comprehensive background in bacterial genetics and metabolism. This will be essential for my career as an infectious disease physician scientist as it will provide me the background needed to understand clinical genetics and metabolomics reports as our ability to characterize both pathogens and the microbiome expands. My laboratory is part of the Center for Staphylococcal Research (CSR) at the University of Nebraska Medical Center which fosters collaboration between faculty studying S. aureus metabolism, genetics, and host-pathogen response. Weekly meetings with members of the CSR will ensure that my understanding of S. aureus pathogenesis extends beyond the perspective of my laboratory. Weekly meetings with my mentor and mentorship from the senior scientists and junior faculty in my laboratory will ensure I have the proper support and training to excel in the field of prokaryotic biology.
HHS’ Tracking Accountability in Government Grants System (TAGGS) website provides access to detailed descriptions of grants, loans, aggregated direct payments and other types of financial assistance awarded by the HHS Operating Divisions (OPDIVs) and the Office of the Secretary Staff Divisions (STAFFDIVs).