aureus with or without functional Fmt were compared. In fact, the MICs of trimethoprim and sulfamethoxazole were 3.5-fold and 3-fold lower, respectively, in Δfmt compared to the parental strain (Figure  4). Complementation with a plasmid-encoded copy of fmt led to partially or fully restored MICs indicating that the increased susceptibility of Δfmt was in fact

a result of lacking formylated proteins. No changes in expression of genes for key enzymes directly involved in the folic acid pathway were observed (Table  1) indicating that the proteins should be produced in equal amounts but may differ in activities leading to altered metabolic fluxes and corresponding differences in antagonist see more susceptibilities. Figure 4 Impact of Δ fmt mutation on the folic acid pathway. (A) Consequences on folic acid metabolism of dihydrofolate reductase (DHFR) inhibition with trimethoprim and dihydropteroate synthetase (DHPS) inhibition with sulfamethoxazole. DHFS stands for dihydrofolate synthase. (B) MICs were determined for the indicated antibiotics. Data represent means ± SEM of at least three independent experiments. *P < 0.05; **P < 0.005; ***P < 0.001 as calculated by the two-tailed Student’s t-test. Discussion Our study demonstrates that the lack of start tRNA ormylation has pleiotropic consequences and affects the global S. aureus exometabolome

and transcriptome in multiple ways. Protein N-termini are usually positively charged but formylated amino groups cannot be protonated any more, which can alter protein conformation and function substantially. We expected that MEK162 manufacturer protein dysfunction resulting from N-terminal charge selleck chemicals llc alteration may affect cellular functions in multiple ways including e.g. by compromising the function of structural proteins, regulators, or enzymes leading to global cellular stress responses, altering regulatory ID-8 networks, or perturbing metabolic pathways, respectively. It has remained

unclear, which S. aureus proteins retain formyl groups upon translation and the activity of which of these may depend on formylation. Our approach set out to assess, which metabolic processes may be compromised in a fmt mutant and we found that many exometabolites were present at similar levels in the wild-type and Δfmt strains while the catabolism of glucose and certain amino acids, the release of pyruvate or pyruvate-derived fermentation products, and the susceptibility to inhibitors of enzymes depending on folic acid derivatives was changed. Thus, protein formylation has distinct roles in certain metabolic pathways. The reduced catabolism of glucose and branched-chain and aromatic amino acids by Δfmt was not reflected by changes in transcription of genes for corresponding enzymes suggesting that these changes did not result from perturbed gene regulation but from compromised abilities of S. aureus to degrade these nutrients.