Examples of inter-strain variability in the production of signal moleculesa in different species.

aZone of induction on agar plate or TLC, or level of induction in liquid assays of a signal molecule reporter strain.bRatio between strain-producing maximal and minimal levels, respectively.cNumber of signal-producing strains considered in the calculation.dTwo additional strains were non-producers.eThree additional strains were non-producers.fEight additional strains were non-producers.gBHL, N-butanoyl-L-homoserine lactone; HHL, N-hexanoyl-L-homoserine lactone; OH-OHL, N-(3-hydroxyoctanoyl)-L-homoserine lactone; OdDHL, N-(3-oxododecanoyl)-L-homoserine lactone; OH-BHL, N-(3-hydroxybutanoyl)-L-homoserine lactone.