The Suf Iron-Sulfur Cluster Biosynthetic System Is Essential in Staphylococcus aureus, and Decreased Suf Function Results in Global Metabolic Defects and Reduced Survival in Human Neutrophils

Abstract

<i>Staphylococcus aureus</i> remains a causative agent for morbidity and mortality worldwide. This is in part a result of antimicrobial resistance, highlighting the need to uncover novel antibiotic targets and to discover new therapeutic agents. In the present study, we explored the possibility that iron-sulfur (Fe-S) cluster synthesis is a viable antimicrobial target. RNA interference studies established that Suf (<u>su</u>l<u>f</u>ur mobilization)-dependent Fe-S cluster synthesis is essential in <i>S. aureus</i> We found that <i>sufCDSUB</i> were cotranscribed and that <i>suf</i> transcription was positively influenced by sigma factor B. We characterized an <i>S. aureus</i> strain that contained a transposon inserted in the intergenic space between <i>sufC</i> and <i>sufD</i> (<i>sufD</i>*), resulting in decreased transcription of <i>sufSUB</i> Consistent with the transcriptional data, the <i>sufD</i>* strain had multiple phenotypes associated with impaired Fe-S protein maturation. They included decreased activities of Fe-S cluster-dependent enzymes, decreased growth in media lacking metabolites that require Fe-S proteins for synthesis, and decreased flux through the tricarboxylic acid (TCA) cycle. Decreased Fe-S cluster synthesis resulted in sensitivity to reactive oxygen and reactive nitrogen species, as well as increased DNA damage and impaired DNA repair. The <i>sufD</i>* strain also exhibited perturbed intracellular nonchelated Fe pools. Importantly, the <i>sufD*</i> strain did not exhibit altered exoprotein production or altered biofilm formation, but it was attenuated for survival upon challenge by human polymorphonuclear leukocytes. The results presented are consistent with the hypothesis that Fe-S cluster synthesis is a viable target for antimicrobial development.