Effects of Quorum Quenching on Biofilm Metacommunity in a Membrane Bioreactor

Quorum quenching (QQ) has received attention for the control of biofilms, e.g., biofilms that cause biofouling in membrane bioreactors (MBRs). Despite the efficacy of QQ on biofouling, it is elusive how QQ influences biofilm formation on membranes. A pilot-scale QQ-MBR and non-QQ-MBR were identically operated for 4 days and 8 days to destructively sample the membranes. QQ prolonged the membrane filterability by 43% with no harmful influence on MBR performance. qPCR showed no effect of QQ on microbial density during either of these time periods. Community comparisons revealed that QQ influenced the bacterial and fungal community structures, and the fungal structure corresponded with the bacterial structure. Metacommunity and spatial analyses showed that QQ induced structural variation rather than compositional variation of bacteria and fungi. Moreover, QQ considerably enhanced the bacterial dispersal across membrane during the early development. As the dispersal enhancement by QQ counteracted the ecological drift, it eliminated the distance-decay relationship, reflecting a neutral theory archetype of metacommunity. Network analyses showed that QQ substantially reduced the amount and magnitude of interactions, e.g., competition and cooperation, for bacteria and fungi, and weakened their network structures, irrespective of time. Additionally, QQ suppressed the growth of specific microbial species (e.g., Acinetobacter), abundant and widespread at the early stage. These findings suggest that QQ influenced the community dynamics at the regional and local levels, correspondingly the ecological selection and dispersal processes, during the biofilm development.