Exogenous Fatty Acids Remodel Staphylococcus aureus Lipid Composition through Fatty Acid Kinase

Abstract

Staphylococcus aureus can utilize exogenous fatty acids for phospholipid synthesis. The fatty acid kinase FakA is essential for this utilization by phosphorylating exogenous fatty acids for incorporation into lipids. How FakA impacts the lipid membrane composition is unknown. In this study, we used mass spectrometry to determine the membrane lipid composition and properties of S. aureus in the absence of fakA. We found the fakA mutant to have increased abundance of lipids containing longer acyl chains. Since S. aureus does not synthesize unsaturated fatty acids, we utilized oleic acid (18:1) to track exogenous fatty acid incorporation into lipids. We observed a concentration-dependent incorporation of exogenous fatty acids into the membrane that required FakA. We also tested how FakA and exogenous fatty acids impact membrane-related physiology and identified changes in membrane potential, cellular respiration, and membrane fluidity. To mimic the host environment, we characterized the lipid composition of wild-type and fakA mutant bacteria grown in mouse skin homogenate. We show that wild-type S. aureus can incorporate exogenous unsaturated fatty acids from host tissue, highlighting the importance of FakA in the presence of host skin tissue. In conclusion, FakA is important for maintaining the composition and properties of the phospholipid membrane in the presence of exogenous fatty acids, impacting overall cell physiology. IMPORTANCE Environmental fatty acids can be harvested to supplement endogenous fatty acid synthesis to produce membranes and circumvent fatty acid biosynthesis inhibitors. However, how the inability to use these fatty acids impacts lipids is unclear. Our results reveal lipid composition changes in response to fatty acid addition and when S. aureus is unable to activate fatty acids through FakA. We identify concentration-dependent utilization of oleic acid that, when combined with previous work, provides evidence that fatty acids can serve as a signal to S. aureus. Furthermore, using mouse skin homogenates as a surrogate for in vivo conditions, we showed that S. aureus can incorporate host fatty acids. This study highlights how exogenous fatty acids impact bacterial membrane composition and function.

Branched chain fatty acid synthesis drives tissue-specific innate immune response and infection dynamics of Staphylococcus aureus

“…This observation implies that de novo BCFA synthesis is predominant during infection and potentially limits bacterial acquisition of UFA. This notion is supported by previous studies indicating that culture of WT S. aureus in the presence of oleic acid (18:1) does not appreciably change BCFA content, as approximately 50% of membrane is still composed of BCFA [11,62]. Furthermore, the sn-2 position of S. aureus phospholipid is exclusively occupied by BCFA in most conditions, implying an established preference for BCFA [9,16,20].…”

Lipidomic and Ultrastructural Characterization of the Cell Envelope of Staphylococcus aureus Grown in the Presence of Human Serum

“…Figure S4 fatty acids were elongated prior to incorporation into diacylglycerolipids. Elongation of exogenously supplemented unsaturated fatty acids has also been observed previously (16,36).…”

“…S3 in the supplemental material) and that SCUFAs can undergo elongation within S. aureus (Fig. S4), suggesting that host-derived fatty acids can fully participate in all fatty acid (FASII) and glycerolipid metabolic pathways (16,36).…”

“…It is generally considered that S. aureus is unable to biosynthesize SCUFAs, and cells grown in the presence of serum (6), liver extract (12), and human low-density lipoprotein (LDL) and egg yolk LDL (13) have been shown to contain significant amounts of SCUFAs in their fatty acid profiles. In addition, free fatty acids are incorporated into phospholipids from medium supplemented with SCUFAs (14)(15)(16). Mass spectrometry (MS) analysis suggests that PG 33:1 is a major phospholipid when S. aureus is grown in the presence of LDL, which is likely made up of C 18:1 Δ9 (oleic acid) at position sn-1 and anteiso C 15:0 at position sn-2 based on MS fragmentation (13,15).…”

Inhibitory effect of Atorvastatin on the secretion of extracellular virulence products by Methicillin resistant Staphylococcus aureus

“…The recent literature citations associated with the emergence of MRSA have reported numerous investigations which had focused on the role of Atorvastatin in combating these hardy virulent MRSA strains (Pruefer Diethard et al, 1999;Adhikari and Novick, 2005;Liu et al, 2005Liu et al, , 2008;DeMars et al, 2020;Wang et al, 2020). Recently it has also been found that statins may have a positive role in treating the symptoms of Coronavirus COVID-19 which is caused by SARS Cov-2 virus.…”