Thin-layer chromatography (TLC) analysis of acyl-homoserine lactones (AHLs) and active quorum-sensing (QS) compounds in dichloromethane supernatant extracts of tryptone yeast–grown Rm1021, 1021Δhfq, and 1021Δhfq pHfq. Each sample corresponding to 1 ml of culture supernatant was spotted on C18 TLC plates, shown by a dashed line. Active QS compounds were detected using an Agrobacterium tumefaciens reporter assay. Spots corresponding to putative AHLs or active QS compounds resolved by TLC in lane 2 are indicated by the letters a to d. AHL standards (right lane) were 500 pmol of 3-oxo-C6-homoserine lactone, 20 nmol of C8-HL (Sigma-Aldrich, Milwaukee, WI, U.S.A.), and 50 nmol of 3-oxo-C16:1-HL (gift from Anatol Eberhard, Cornell University, Ithaca, NY, U.S.A.). This experiment was repeated twice with results similar to those shown here.