Macroscopic observations of swarming in WT R. etli (A and B) and cinR mutant (C–H) on plates containing synthetic AHLs. The plates are supplied with 3OH-(slc)-HSL (×1) (B and D), C10-HSL (100 μM, F; 25 μM, G), and C14-HSL (20 μM, H). For 3OH-(slc)-HSL extraction see Materials and Methods. For swarming, the solvent effect was studied in the presence of the corresponding amounts of acetonitrile (E) or when appropriate an extract from the strain devoid of the cin locus (C). The control plates never affected swarming positively or negatively in R. etli. X, the concentration factor of 3OH-(slc)-HSL compared with the supernatant concentration of the producer strain. Diameter of the swarm plate is 6 cm. + corresponds to swarming; − corresponds to a negative swarming phenotype.