Bacterial assembly and succession during aerobic granulation stimulated by Fe3O4 nanoparticles with real municipal wastewater: The role of acyl-homoserine lactones mediated communication

The acceleration of aerobic granule formation stimulated by Fe 3 O 4 nanoparticles (Fe 3 O 4 NPs) has received considerable attention, but optimal dosing strategy and in-depth microbial mechanism remain poorly understood. In this study, granule cultivation was performed with different dosing frequencies of 50 mg/L Fe 3 O 4 NPs using real municipal wastewater as influent. Acyl-homoserine lactones (AHLs) distribution and dynamics of AHLs-related consortia and functional genes, as well as core taxa in coexisting diameter heterogenous granules were explored to provide foundational information on quorum sensing (QS) regulation of microbial evolution for granulation. Results showed that dosing Fe 3 O 4 NPs every five days achieved the fastest granulation. Fe 3 O 4 NPs addition was significantly correlated with AHLs distribution. Both extracellular polymeric substances and AHLs concentrations significantly decreased in the largest granules with particle size >0.8 mm ( p < 0.02). Based on core taxa analysis, bacterial assembly and succession during conversion from flocs to granules were found that 11 keystone genera significantly enriched and six genera gradually decreased as granule development. AHLs-based quorum quenching (QQ) bacteria and QS bacteria gradually enriched in the larger granules, accompanied with decrease of AHLs synthesis and receptor genes and increase of AHLs lactonase genes. Co-occurrence network analyses indicated that QQ bacteria, rather than QS bacteria, communicated more frequently with core taxa during granulation. The potential cooperations between QQ and QS bacteria, as well as QQ bacteria and keystone genera were enhanced associated with granular growth. The results of this study suggest that the role of AHLs-mediated QQ in granulation may be overlooked. • Dosing Fe 3 O 4 NPs every five days achieved the fastest granulation. • Both EPS and AHLs contents significantly decreased in the largest granule fraction. • AHLs-QQ bacteria, as well as QS bacteria, gradually enriched in the larger granules. • AHLs-QS genes decreased and AHLs lactonase genes increased in larger granules. • QQ bacteria communicated more frequently with core taxa during granulation.