Community quorum sensing signalling and quenching: microbial granular biofilm assembly

RESULTS:Our data revealed a distinct difference between the QS and QQ potentials of the two communities, with different species largely displaying either QS or QQ functions. Thefloccular sludge community showed a high rate of QQ activity, and this rate was dependent on the acyl chain length demonstrating specificity of degradation. When thefloccular biomass was transformed into the granular sludge, the QQ activity of the community was reduced by 30%.N-acyl homoserine lactones with four to eight carbons on the acyl chain accumulated at the granular stage, and their concentrations were at least threefold higher than those of thefloccular stage. Thesefindings corroborated meta-community analysis where a major shift in the dominant species from potential signal quenchers to producers was observed during the transition fromflocs to granules, indicating the role of species composition and associated signalling activities in coordinating community behaviours. CONCLUSIONS:This study suggests that QQ has an important function in regulating community level QS signalling, and provides a mechanistic insight into the role of QS biology in complex community assembly.