Figure 3.

The role of aromatic amino acid biosynthesis genes in resistance to H₂O₂. (A) Schematic representation of aromatic amino acid biosynthesis pathway, adapted from the KEGG pathway database. The genes in red color were identified by the Tn-seq analysis as conditionally essential for H₂O₂ resistance in Salmonella. The genes in bold type indicated that the mutant phenotype was also validated by individual mutant assay. (B) The overnight cultures of the individual mutants were diluted 1:200 in LB (no H₂O₂) and LB containing either 2.5 mM H₂O₂ (H₂O₂L) or 3.5 mM H₂O₂ (H₂O₂H). The cultures were incubated at 37 °C for 24 h in a 96-well plate. The growth curves are shown LB (blue), H₂O₂L (red), and H₂O₂H (green). In the growth curve of ΔaroK, the red color is overlapped with the green color. (C) Upregulation of Salmonella proteins in response to H₂O₂L in comparison to LB. Wild type S. Typhimurium strain was grown in LB, H₂O₂L, and H₂O₂H until mid-exponential phase. Targeted-proteomics was used to quantify AroB, AroE_2, AroK, and AroA protein expressions in response to H₂O₂L.