Bacillithiol has a role in F e– S cluster biogenesis in S taphylococcus aureus

Summary S taphylococcus aureus does not produce the low‐molecular‐weight ( LMW ) thiol glutathione, but it does produce the LMW thiol bacillithiol ( BSH ). To better understand the roles that BSH plays in staphylococcal metabolism, we constructed and examined strains lacking BSH . Phenotypic analysis found that the BSH ‐deficient strains cultured either aerobically or anaerobically had growth defects that were alleviated by the addition of exogenous iron ( F e) or the amino acids leucine and isoleucine. The activities of the iron–sulfur ( F e– S ) cluster‐dependent enzymes LeuCD and IlvD , which are required for the biosynthesis of leucine and isoleucine, were decreased in strains lacking BSH . The BSH ‐deficient cells also had decreased aconitase and glutamate synthase activities, suggesting a general defect in F e– S cluster biogenesis. The phenotypes of the BSH ‐deficient strains were exacerbated in strains lacking the F e– S cluster carrier Nfu and partially suppressed by multicopy expression of either sufA or nfu , suggesting functional overlap between BSH and F e– S carrier proteins. Biochemical analysis found that SufA bound and transferred F e– S clusters to apo‐aconitase, verifying that it serves as an F e– S cluster carrier. The results presented are consistent with the hypothesis that BSH has roles in F e homeostasis and the carriage of F e– S clusters to apo‐proteins in S . aureus .