Graduation Date
Fall 12-19-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Programs
Immunology, Pathology & Infectious Disease
First Advisor
Paul Fey
Abstract
Staphylococcus aureus (S. aureus) is the most common pathogen associated with skin and soft tissue infections (SSTI), costing Americans over $13 billion per year. To successfully establish a SSTI, glycolytic activity is required, indicating carbon catabolite repression (CCR) via CcpA is active. CcpA represses secondary carbon sources such as amino acids to ensure the preferential utilization of glucose. This is observed during growth in chemically defined medium with glucose (CDMG), where S. aureus requires supplementation with arginine, since CcpA represses arginine biosynthesis and renders the bacteria auxotrophic for arginine. Therefore, during the establishment of an infection S. aureus relies on the transport of arginine. The S. aureus USA300 genome harbors two arginine/ornithine antiporters, ArcD1 and ArcD2, localized to distinct copies of the arginine deaminase operons. In these studies, inactivation of both transporters did not impair growth, demonstrating they are not required for utilizing arginine as a carbon source. To identify novel arginine transporters, ArgT, we performed a suppressor screen using the toxic arginine analog, canavanine. A radiolabeled transport assay verified ArgT transports arginine, however qRT-PCR indicated the gene is repressed in the presence of glucose by CcpA. These results suggest ArgT is not responsible for the transport of arginine during the establishment of an infection when glucose is present, therefore additional library screens were performed. Growth of mutants from the Nebraska Transposon Mutant Library (NMTL) were analyzed in media supplemented with or without glucose, under conditions dependent on the transport of arginine, or the arginine precursors citrulline and ornithine. Additionally, RNA sequencing was utilized to reveal permease transcripts that were induced under conditions when arginine transport was essential for growth. These methods identified GlnPQ, SAUSA300_2265, SAUSA300_1231, SAUSA300_1642, and SAUSA300_1628 as potential arginine transporters. Growth analysis indicates that AhrC regulates additional transporters, with regulation varying across different media conditions. The comprehensive identification of S. aureus arginine transporters will enable insight into the temporal and spatial dynamics of arginine acquisition during infection, contributing to a deeper understanding of the organisms pathogenesis strategies.
Recommended Citation
Schulze, Gabrielle, "Staphylococcus aureus Encodes Multiple Arginine Transporters" (2025). Theses & Dissertations. 996.
https://digitalcommons.unmc.edu/etd/996
Comments
2025 Copyright, the authors