TLC of autoinducers synthesized by a wild-type A. tumefaciens strain. (A) Lane 1 represents the activities of autoinducers obtained from 100 μl of culture supernatant. Lanes 2 to 8 show fivefold serial dilutions of the sample chromatographed in lane 1. (B) Synthetic racemic autoinducers. Lane 1 contains 50 pmol of 3-oxo-C6-HSL, 50 pmol of 3-oxo-C8-HSL, and 1,500 pmol of 3-oxo-C12-HSL. Lanes 2 to 8 show fivefold serial dilutions of the sample chromatographed in lane 1. (C) Conversion of 3-oxo-C8-HSL and 3-oxo-C6-HSL to a more polar active form by treatment with alkali. Lane 1, 3-oxo-C8-HSL incubated at pH 7.0; lane 2, 3-oxo-C8-HSL incubated at pH 12 for 1 h; lane 3, 3-oxo-C8-HSL incubated at pH 13 for 1 h; lane 4, autoinducers produced by strain R10(pCF372); lane 5, 3-oxo-C6-HSL incubated at pH 13 for 1 h; lane 6, 3-oxo-C6-HSL incubated at pH 12 for 1 h; lane 7, 3-oxo-C6-HSL incubated at pH 7.