Abstract
Although N-acyl-L-homoserine lactone (AHL) based quorum sensing (QS) phenomenon has been observed in mature anaerobic granules, the biological role of AHL-based QS system in anaerobic granulation process remains unexplored. For the first time, a long-term anaerobic bioreactor was operated for 168 days to investigate the biological role of AHL in the granulation process which was divided into three phases (phase I: floccular, phase II: granulation, phase III: maturation). Two different AHLs including C8-HSL and C10-HSL were characterized at nanogram levels. The AHL level was elevated over 20-fold and strongly positively correlated with extracellular polymeric substances (EPS) production and sludge particle size during phase I-II. Exogenous addition of AHL to the floccular sludge also resulted in significantly increased EPS production. Metadata analysis suggested that the granulation process was accompanied by an increase in the abundance of QS-relevant microorganisms. The strong relationships (R > 0.9233, p < 0.01) among AHL concentrations, EPS (except loosely bound EPS), granulation and community variation indicated that AHL-mediated QS played an important role in coordinating community level behaviors associated with granulation, potentially through the regulation of EPS production and composition. This study gives a deep insight into the underlying QS-relevant mechanism of anaerobic granulation process.
Highlights
In the past years, increasing attention has been paid to the quorum sensing (QS) in wastewater treatment systems such as membrane bioreactors (MBRs)[1,2], sequencing batch reactors[3], granular sludge[4], and anaerobic ammonium oxidation (Anammox)[5,6]
Our previous study reported that C8-homoserine lactone (C8-HSL) and C10-HSL were widely identified in all the collected anaerobic granules and 12 different microbes were speculated to be regulated by acyl-L-homoserine lactone (AHL) to participate in the secretion of extracellular polymeric substances (EPS)[13]
By employing ecology study approaches to statistically analyze the acquired chemical and biological data, we explored the biological role of AHL signaling activity in the assembly and interaction of highly diverse community during the anaerobic granulation process
Summary
In the past years, increasing attention has been paid to the quorum sensing (QS) in wastewater treatment systems such as membrane bioreactors (MBRs)[1,2], sequencing batch reactors[3], granular sludge[4], and anaerobic ammonium oxidation (Anammox)[5,6]. Our previous study reported that C8-homoserine lactone (C8-HSL) and C10-HSL were widely identified in all the collected anaerobic granules and 12 different microbes were speculated to be regulated by AHL to participate in the secretion of extracellular polymeric substances (EPS)[13]. These studies mainly investigated the diversity, distribution and function of AHL in mature anaerobic granules. As the sludge granulation is a consequence of self-immobilized microbial aggregation, investigating the biological impact of AHL-based QS on microbial community organization and intercellular cooperation during granulation period is of great importance for understanding the microbial foundation of anaerobic granulation process. By employing ecology study approaches to statistically analyze the acquired chemical and biological data, we explored the biological role of AHL signaling activity in the assembly and interaction of highly diverse community during the anaerobic granulation process
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