Staphylococcus aureus can degrade exogenous fatty acids through β-oxidation

Staphylococcus aureus has long been thought to lack a functional fatty acid degradation (Fad) pathway despite the presence of a locus annotated with the necessary fad genes; however, two recent studies have examined the fad operon for the first time. While they provided key insights about the system and both identified that exogenous fatty acids can be added to coenzyme A to produce an acyl-CoA, neither identified whether degradation occurs. The fad operon contains two sizeable intergenic regions even though the fadXDEBA genes can be expressed on a single polycistronic mRNA under the control of the fadX promoter. We hypothesized that these intergenic regions could be a point of regulation that prevents full Fad function; therefore, we generated a new S. aureus strain where the two intergenic regions of the fadXDEBA operon were deleted. Using mass spectrometry analysis with this strain, we detected degradation products from both palmitic acid and oleic acid, a saturated and unsaturated fatty acid, respectively. The products were absent in a fadXDEBA mutant. These data demonstrate that the S. aureus fatty acid degradation system is functional and can degrade exogenous fatty acids.IMPORTANCEThere have been limited studies on the fatty acid degradation (Fad) pathway of Staphylococcus aureus. The fadXDEBA operon has been shown to contain all the genes necessary for β-oxidation, and the FadD and FadBA proteins have been shown to perform their canonical functions. This study demonstrates that the full S. aureus Fad pathway is functional and capable of degrading exogenous fatty acids. These data bring to light a second exogenous fatty acid utilization pathway, expanding our knowledge on how this pathogen metabolizes environmental fatty acids.