DescriptionStaphylococcus aureus is a public health concern. It can evade the immune system and develop resistance to many antibiotic classes. The human immune system employs diverse mechanisms to overcome S. aureus infections including disrupting iron (Fe) and copper (Cu) homeostasis at the host-pathogen interface. The work presented herein described iron-sulfur (Fe-S) cluster synthesis as a potential antimicrobial target. We demonstrated that Suf (sulfur mobilization)-dependent Fe-S cluster synthesis is essential in S. aureus. Importantly, the Suf system is not present in mammals suggesting that it is a promising antibiotic target. A strain with decreased suf transcription exhibited phenotypes that are associated with impaired Fe-S protein maturation. These phenotypes included a reduction in the activity of Fe-S cluster-dependent enzymes and growth inhibition in media deficient in metabolites that require Fe-S enzymes for synthesis. The impairment in Fe-S cluster biogenesis led to increased sensitivity to reactive oxygen and reactive nitrogen species and decreased survival in human polymorphonuclear leukocytes. We explored how copper harm S. aureus, by creating a ΔcopAB ΔcopBL strain (cop-) that was defective in removing copper from the cytosol. We isolated cop- strains with Tn insertions in mntABC that resist copper. When cultured with copper, strains containing the mntA::Tn mutation had less copper load than the parent strains. Manganese bound MntR repressed MntABC. The ?mntR strain had reduced growth and increased copper load under copper stress. The introduction of the mntA::Tn allele annulled these phenotypes. Over-expression of MntABC amplified cellular copper load and sensitivity to copper. The mntA::Tn mutation presence also protected Fe-S enzymes from inactivation by copper. We also found that copper was not substantially inhibiting the growth of S. aureus by poisoning NrdEF under the growth conditions utilized; however, when NrdEF function was decreased by copper, the ribonucleotide reductase function is decreased by the addition of hydroxyurea. The introduction of a mntA::Tn allele improved growth of both ΔcopAZ and ΔcopBL strains from copper intoxication suggesting that the presence of a second copper detoxification system protects S. aureus from MntABC-dependent copper intoxication. The data presented are consistent with a model wherein copper enters S. aureus cells via the MntABC importer and poisons Fe-S enzymes. Taken together, the work presented in this thesis supports the viability of targeting Fe-S synthesis as a viable therapeutic approach and established a novel role for mntABC in copper homeostasis.