Role of N-acyl-homoserine lactone (AHL) based quorum sensing on biofilm formation on packing media in wastewater treatment process

Quorum sensing (QS) signaling has been extensively studied in granules and single species populations. However, the knowledge regarding QS in biofilm formation on packing media has neither been experimentally explored nor theoretically addressed. We performed a long-term study to investigate the links between QS, organization and composition of complex microbial communities when biofilm developed on packing media. Three distinct phases were defined according to the weight of the biofilm and the removal rate of COD and ammonia nitrogen. Four kinds of N-acyl-homoserine-lactone (AHL) were found to be regularly and positively correlated with biofilm in growth stage (activation phase) (p < 0.01), while the correlation was not significant in other phases. Total AHL level was also closely related to the productions of extracellular polymeric substance (EPS), especially in polysaccharide. Sequence analysis results revealed that community structure changed with growth of biofilm, and top 34 most abundant community members had a significant correlation with AHLs production. Notably, biofilm and production of EPS, as well as community structure changed after dosing with nanomolar level of exogenous AHL in stable and mature biofilm, but this change was not a signal concentration-dependent manner. This study provides a foundation for investigation of QS effect on biofilm formation on packing media in many natural and engineered ecosystems, where it coordinates community behavior.