Graduation Date

Fall 12-16-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Pathology & Microbiology

First Advisor

Dr. Paul D. Fey

Abstract

Staphylococcus aureus must rapidly adapt to a variety of carbon and nitrogen sources during invasion of a host. Within a staphylococcal abscess, preferred carbon sources such as glucose are limiting, suggesting S. aureus survives through the catabolism of secondary carbon sources. S. aureus encodes pathways to catabolize multiple amino acids including those that generate pyruvate, 2-oxoglutarate, and oxaloacetate. To assess amino acid catabolism, S. aureus JE2 and mutants were grown in complete defined medium containing 18 amino acids but lacking glucose (CDM). A mutation in glutamate dehydrogenase (gudB), which generates 2-oxoglutarate from glutamate, abrogated growth in CDM suggesting that glutamate and those amino acids generating glutamate, particularly proline, serve as the major carbon source in this media. Nuclear Magnetic Resonance (NMR) studies confirmed this hypothesis. Furthermore, a mutation in acetate kinase (ackA) also abrogated growth of JE2 in CDM suggesting that ATP production from pyruvate-producing amino acids is also critical for growth. In addition, although a functional respiratory chain was absolutely required for growth, the relative oxygen consumption rate and intracellular ATP concentration were significantly lower during growth in CDM when compared to growth in glucose-containing media. Finally, transcriptional analyses demonstrated that genes coding for the enzymes that synthesize glutamate from proline, arginine and histidine are repressed by CcpA and carbon catabolite repression. We also demonstrated that in the absence of CcpA repression, the global transcriptional regulator, CodY, functions to positively regulate proline catabolism by activating putA expression. The arginine transcriptional regulator, ArgR1, also functions to positively regulate putA expression, while the arginine transcriptional regulators, ArgR2 and AhrC, are functioning to repress arginine biosynthesis via argG; presumably in the presence of arginine. These data demonstrate that pathways important for glutamate catabolism and ATP generation via Pta/AckA are important for growth in niches where glucose is not abundant.

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