HPLC profiles of 14C-AHLs synthesized by (A) Pseudomonas aeruginosa PAO1 [25] (labeled for 30 min), (B) Pseudomonas chloroaphis GM17 [26] (labeled for 2 hours), and (C) Bradyrhizobium japonicum USDA110 [27] (labeled for 1 day). In all graphs the x-axis indicates the fraction numbers that were collected over a 10–100% methanol-in-water gradient. The left y-axis denotes the counts per minute (CPM) of radiolabel in each fraction (black circles) and the right y-axis indicates the methanol concentration of the HPLC run (dashed line). The synthetic AHL compound that co-elutes with the observed radiolabel peak is abbreviated as follows: butanoyl-HSL (C4), 3-oxo-dodecanoyl-HSL (3OC12), 3-hydroxy-hexanoyl-HSL (3OHC6), 3-hydroxy-octanoyl-HSL (3OHC8), 3-hydroxy-decanoyl-HSL (3OHC10), and isovaleryl-HSL (IV). Radioactivity that eluted in the column void volume (fraction 4) is presumed to be unincorporated methionine.