Outcompeting Presence of Acyl-Homoserine-Lactone (AHL)-Quenching Bacteria over AHL-Producing Bacteria in Aerobic Granules

The roles of acyl-homoserine-lactone (AHL)-based quorum sensing in biofilm formation for biological wastewater treatment have been widely recognized. In previous studies about the role of AHLs in biofilm formation, the focus is always on AHL-producing bacteria, while attention to AHL-quenching bacteria is not paid. In this work, 600 microbial isolates were screened from aerobic granules, a special type of biofilm, based on their AHL-producing or -quenching ability. The isolates with quenching activity were mainly <i>Rhodococcus</i> sp.; others included <i>Sphingopyxis</i> sp. and <i>Bacillus</i> sp. This result indicates the outcompeting presence of AHL-quenching bacteria over AHL-producing bacteria and a high complexity of AHL-based communication in the aerobic granules and also implies the possible overlooking of the role of AHLs in biofilm formation in previous studies