2.6. Detection of AHL by Thin-Layer Chromatography (TLC)

Twenty μL aliquots of extracts were loaded onto TLC plates as described in Pinto [9]. A volume of 150 mL of soft agar at 42°C was mixed with 30 mL of the monitor strain E. coli MT102 (pSB403) or C. violaceum CV026. The added soft agar of the appropriated monitor strain was dispensed onto TLC plate receiving a 2 to 3 mm thick layer. After 20 min, the plate was put in an airproof box with a wet paper inside and incubated overnight at 30°C.

The documentation was dependent on the monitor strain used. For C. violaceum CV026, the material was incubated until 48 h and the signal molecules could be identified by forming violet pigmented spots. When E. coli MT102 pSB403 was the monitor, the material was incubated overnight at 30°C and put into a dark box and the bioluminescence was detected with a highly sensitive photon-counting camera (C2400-40; Hamamatsu Photonics Herrsching, Germany).