cis-.DELTA.2-11-methyl-Dodecenoic acid is a diffusible signal factor (DSF) in extracellular microbial and fungal communication systems. In a DSF bioassay, the minimum concentration of cis-.DELTA.2-11-methyl-dodecenoic acid required for induction of a DSF biosensor was about 0.5 µM, which is…