Deciphering the potential role of quorum quenching in efficient aerobic denitrification driven by a synthetic microbial community.

Low efficiency is one of the main challenges for the application of aerobic denitrification technology in wastewater treatment. To improve denitrification efficiency, a synthetic microbial community (SMC) composed of denitrifiers Acinetobacter baumannii N1 (AC), Pseudomonas aeruginosa N2 (PA) and Aeromonas hydrophila (AH) were constructed. The nitrate (NO ₃ ^- -N) reduction efficiency of the SMC reached 97 % with little nitrite (NO ₂ ^- -N) accumulation, compared to the single-culture systems and co-culture systems. In the SMC, AH proved to mainly contribute to NO ₃ ^- -N reduction with the assistance of AC, while PA exerted NO ₂ ^- -N reduction. AC and AH secreted N-hexanoyl-DL-homoserine lactone (C ₆ -HSL) to promote the electron transfer from the quinone pool to nitrate reductase. The declined N-(3-oxododecanoyl)-L-homoserine lactone (3OC ₁₂ -HSL), resulting from quorum quenching (QQ) by AH, stimulated the excretion of pyocyanin, which could improve the electron transfer from complex III to downstream denitrifying enzymes for NO ₂ ^- -N reduction. In addition, C ₆ -HSL mainly secreted by PA led to the up-regulation of TCA cycle-related genes and provided sufficient energy (such as NADH and ATP) for aerobic denitrification. In conclusion, members of the SMC achieved efficient denitrification through the interactions between QQ, electron transfer, and energy metabolism induced by N-acyl-homoserine lactones (AHLs). This study provided a theoretical basis for the engineering application of synthetic microbiome to remove nitrate wastewater.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2024. Published by Elsevier Ltd.)