The attachment potential and N-acyl-homoserine lactone-based quorum sensing in aerobic granular sludge and algal-bacterial granular sludge
Bacteria and algae often coexist in the aerobic granular sludge (AGS) system in a photo-bioreactor, forming algal-bacterial granular sludge. In this study, the physicochemical characteristics and microbial attachment potential of the AGS and algal-bacterial granular sludge were comparatively analyzed. Results clearly showed that the larger and denser algal-bacterial granular sludge had stronger attachment potential compared to the AGS (as the control). A bioassay with Agrobacterium tumefaciens KYC55 indicated that N-acyl-homoserine lactones (AHLs) existed in both sludge types, but further investigations revealed that the relative AHL content of the algal-bacterial granular sludge obviously increased and slightly decreased during phases II and III, respectively, but was consistently higher than the AGS. Based on the EPS measurements and 3D-excitation-emission matrix (3D-EEM) fluorescence spectra analysis, the enhancement of AHL-based QS favored the hydrophobic protein production of algal-bacterial granular sludge, contributing to a good development of the granular sludge. In addition, it was also found that inhibition of AHLs resulted in the reduction of the protein content and attachment potential in algal-bacterial granular sludge, which was unfavorable to the structural stability of the granules. High-throughput sequencing analysis showed that the microbial community of AGS was different from the algal-bacterial granular sludge; specifically, algal-bacterial granulation facilitated the abundance of AHLs and EPS producers, such as the genera Acinetobacter, Chryseobacterium, and Flavobacterium.
KeywordsAlgal-bacterial granules Quorum sensing (QS) N-acyl-homoserine lactone (AHL) Attachment potential Extracellular polymeric substances (EPS)
The authors would like to show our sincerely gratitude for Prof. Hui Wang in Nanjing Agricultural University for providing Agrobacterium tumefaciens KYC55 (pJ372) (pJ384) (pJ410). This work was financed by the National Natural Science Foundation of China (51778172), State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (2016DX11), and the Nanqi Ren Studio, Academy of Environment & Ecology, Harbin Institute of Technology.
Compliance with ethical standards
This article does not contain any studies with human participants or animals performed by any of the authors.
Conflict of interest
The authors declare that they have no competing interests.
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