Identification of 2-undecanone in P. aeruginosa-infected mouse peritoneal fluid. (A) Schematic figure of sample preparation for GC-MS analysis. (B) A representative GC-MS sample spectrum of 2-undecanone (2-Und) from the PAO1-infected sample and (C) library spectrum. (D) The structure of 2-undecanone and a representative extracted ion chromatogram overlay of the 2-undecanone peak. 2-Undecanone was only identified in the PAO1-infected sample (red line). (E) GC-MS standard curve based on 10-fold series of 2-undecanone. (F) The quantified levels of 2-undecanone in PAO1-infected mouse peritoneal fluid.