Role of N-acyl homoserine lactone (AHL)-based quorum sensing (QS) in aerobic sludge granulation.

N-acyl homoserine lactone (AHL)-based quorum sensing (QS) has been recognized to play an important role in the formation of biofilm. However, aerobic granular sludge is considered as a special biofilm, and its biological implication and role of AHL-based QS still remain unclear. This study investigated the role of AHL-based QS in aerobic granulation. Results showed that AHLs were necessary to the typical aerobic granulation, and AHL-associated coordination of bacteria in sludge aggregation was sludge density dependent only when it reached a threshold of 1.010 g/mL; AHL-based QS was activated to regulate aerobic granulation. Furthermore, a quorum quenching method was firstly adopted to investigate the role of AHLs in aerobic granules. Results showed inhibition of AHL by acylase that reduced the AHL content in aerobic granules and further weakened its attachment potential, which proved that AHLs play an important role in the formation of aerobic granules. Additionally, the assay of quorum quenching not only proved that AHL-based QS could regulate EPS production but also provided additional evidence for the role of AHLs in aerobic granulation by regulating EPS content and its component proportion.