Polyunsaturated fatty acids: host-derived antimicrobials against glycolytic Staphylococcus aureus

ABSTRACT Metabolic flexibility allows Staphylococcus aureus to survive killing by antibiotics and antimicrobial immune molecules while infecting every niche of the mammalian host. Whether S. aureus is using glycolysis, aerobic respiration, or anaerobic respiration to generate energy, these cellular processes must be accurately attuned to the infected host tissue. Shifting from respiration to glycolysis lowers metabolic throughput, allowing the transition to a persistent S. aureus infection and avoiding killing by most antimicrobial molecules, which typically target rapidly dividing cells. Previously, we reported that arachidonic acid (AA), an abundant host polyunsaturated fatty acid (PUFA), kills S. aureus through a lipid peroxidation mechanism. Here, we report that the extent of PUFA killing of S. aureus can be predicted by the autoxidation rate constant, extending our previous AA findings to include all PUFAs. Contrasting many other antimicrobial molecules, AA kills glycolytic S. aureus more effectively than respiring S. aureus . Elevating cellular ATP levels protects S. aureus from PUFA killing, indicating that glycolytic S. aureus strains cannot sufficiently energize the ATP-dependent processes that allow S. aureus to survive PUFA toxicity. This report defines cellular metabolism as a key determinant in S. aureus PUFA resistance and demonstrates that PUFAs are effective antimicrobials against glycolytic S. aureus , including persister cells and small colony variants. Furthermore, identifying and validating the ATP-dependent processes that protect S. aureus from PUFA killing will define pathways that can be targeted to accentuate killing by the host immune system, leading to the clearance of persistent S. aureus infections. IMPORTANCE Staphylococcus aureus causes significant human morbidity and mortality. The metabolic diversity of this pathogen makes eradication challenging, leading to persistent infections in many patient populations. Polyunsaturated fatty acids (PUFAs) are host-derived antimicrobial molecules that are abundant at the host-pathogen interface. Here, we define the mechanism of killing by PUFAs in metabolically limited S. aureus strains. These strains are difficult to eradicate because most therapies target rapidly dividing cells. We demonstrate that PUFAs kill slow-growing S. aureus through a lipid peroxidation mechanism better than their normal growth counterparts. Restoring ATP levels in these strains protects against PUFA killing, demonstrating that the PUFA survival response is not fully energized in the low metabolic state.