Redirection of Metabolism in Response to Fatty Acid Kinase in Staphylococcus aureus

Abstract

is capable of phosphorylating exogenous fatty acids via the fatty acid kinase FakA for incorporation into the bacterium's membrane. Additionally, FakA plays a significant role in virulence factor regulation and skin infections. We previously showed that a mutant displays altered growth kinetics observed during late-exponential phase of growth. Here, we demonstrate that the absence of FakA leads to key metabolic changes. First, the mutant has an altered acetate metabolism with acetate being consumed at an increased rate than the wild-type strain. Moreover, the growth benefit was diminished with inactivation of the acetate-generating enzyme AckA. Using a mass spectrometry-based approach, we identified altered concentrations of TCA cycle intermediates and both intracellular and extracellular amino acids. Together, these data demonstrate a change in carbohydrate carbon utilization and altered amino acid metabolism in the mutant. Energy status analysis revealed the mutant had a similar ADP/ATP ratio, but reduced adenylate energy charge. The inactivation of changed the NAD+/NADH and NADP+/NADPH ratio, indicating a more oxidized cellular environment. Evidence points towards the global metabolic regulatory proteins CcpA and CodY being important contributors for the altered growth in a mutant. Indeed, it was found that directing amino acids from the urea cycle into the TCA cycle via glutamate dehydrogenase was an essential component of growth after glucose depletion. Together, this data identifies a previously unidentified role for FakA in the global physiology of that links external fatty acid utilization and central metabolism. The fatty acid kinase, FakA, of plays several important roles in the cell. FakA is important for the activation of the SaeRS two-component system and secreted virulence factors like α-hemolysin. However, the contribution of FakA to cellular metabolism has not been explored. Here, we highlight the metabolic consequence of removal of FakA from the cell. The absence of FakA leads to altered acetate metabolism, altered redox balance, as well as a change in intracellular amino acids. Additionally, the use of environmental amino acids sources is affected by FakA. Together, these results demonstrate for the first time that FakA provides a link between the pathways for exogenous fatty acid use, virulence factor regulation, and other metabolic processes.

DNA Binding and Sensor Specificity of FarR, a Novel TetR Family Regulator Required for Induction of the Fatty Acid Efflux Pump FarE in Staphylococcus aureus

“…This may be due to the pleiotropic phenotype ascribed to USA300 ΔfakA, including an elevated pool of nonesterified fatty acids, leading to reduced transcription of the SaeRS two-component regulator and defective production of Hla toxin (32)(33)(34). Broader metabolic changes were also noted, including altered carbon and amino acid metabolism (35). An elevated basal expression of farE in response to accumulation of cellular metabolites would be consistent with observations that other RND family efflux pumps also exhibit increased expression in response to an accumulation of cellular metabolites (36)(37)(38)(39).…”

The DEAD-box RNA helicase CshA is required for fatty acid homeostasis in Staphylococcus aureus

“…FakA, along with its lipid binding partners, phosphorylates free fatty acids and is essential for both incorporation of exogenous fatty acids and fatty acid turnover [ 18 , 34 ]. It was recently reported that its inactivation alters acetate metabolism by an unknown mechanism [ 35 ], which would explain its occurrence in the screen as favoring the redirection of acetyl-CoA flow towards acetate production rather than SCFA. The ltaS gene encodes the lipoteichoic acid synthetase responsible for lipoteichoic acid (LTA) synthesis [ 36 ].…”

“…aureus [ 34 ]. A recent report and particularly interesting study in light of our own showed that inactivation of fakA impacts the acetate switch, resulting in high secretion of acetate during exponential growth [ 35 ]. We can thus propose that fakA mutations help ΔcshA growth through the redirection of acetyl-CoA flow away from SCFA synthesis.…”

A FAS solution to a DEAD case

“…FakA depletion leads to free fatty acid accumulation that may modify S . aureus regulation and FASII activity and alter acetate utilization [ 5 , 6 ]. How the slowdown of FASII synthesis adjusts fatty acid membrane composition and fluidity is a new open question arising from this work.…”