A series of 22 novel synthetic N-acyl-homoserine lactone analogues has been evaluated for both their inducing activity and their ability to competitively inhibit the action of 3-oxo- hexanoyl-l-homoserine lactone, the natural inducer of bioluminescence in the bacterium Vibrio fischeri. In the newly synthesized analogues, the extremity of the acyl chain was modified by introducing ramified alkyl, cycloalkyl or aryl substituents at the C-4 position. ...