ABSTRACTStaphylococcus aureusis capable of phosphorylating exogenous fatty acids for incorporation into the bacterium's membrane via the fatty acid kinase, FakA. Additionally, FakA plays a significant role in virulence factor regulation and skin infections. We previously showed that afakAmutant displays altered growth kineticsin vitro, observed during the late-exponential phase of growth. Here, we demonstrate that the absence of FakA leads to key metabolic changes. First, thefakAmutant has an altered acetate metabolism, with acetate being consumed at an increased rate than in 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 tricarboxylic acid (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 thefakAmutant. Energy status analysis revealed the mutant had a similar ADP/ATP ratio to that of the wild type, but a reduced adenylate energy charge. The inactivation offakAchanged the NAD+/NADH and NADP+/NADPH ratios, indicating a more oxidized cellular environment. Evidence points to the global metabolic regulatory proteins CcpA and CodY being important contributors to the altered growth in afakAmutant. Indeed, it was found that directing amino acids from the urea cycle into the TCA cycle via glutamate dehydrogenase was an essential component ofS. aureusgrowth after glucose depletion. Together, these data identify a previously unidentified role of FakA in the global physiology ofS. aureus, linking external fatty acid utilization and central metabolism.IMPORTANCEThe fatty acid kinase, FakA, ofStaphylococcus aureusplays 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 and altered redox balance, as well as a change in intracellular amino acids. Additionally, the use of environmental amino acid 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.
Structure-function relationships among wild-type variants of Staphylococcus aureus beta-lactamase: importance of amino acids 128 and 216.
