Efficient nitrogen removal of mangrove constructed wetlands: Enhancing heterotrophic nitrification-aerobic denitrification microflora through quorum sensing

There are a large number of heterotrophic nitrifying aerial denitrifying (HN-AD) bacteria in mangrove wetlands. They have a certain salt tolerance and high nitrogen removal potential. In addition, quorum sensing (QS) can enhance the denitrification and biofilm formation ability of HN-AD bacteria, further improving wetlands’ denitrification efficiency. In this study, five HN-AD bacteria were screened from a mangrove wetland system, and it was discovered that the Vibrio sinaloensis strain W37 has a QS function and can produce C8-HSL. The QS effect of W37 can promote the growth (OD600 increased by 0.02–0.32), denitrification (increased efficiency of 0.74–24.63%) and biofilm formation (extracellular polymeric substances increased by 7.95–42.02 mg/L) in Achromobacter pulmonis strain E43, Zobellella denitrificans strain A36, Pseudomonas Oleovorans strain F2, and Achromobacter xylosoxidans Strain J1. As a result, HN-AD microflora was developed and added to mangrove constructed wetlands. Results showed that the addition of the microflora enhanced the nitrogen removal capacity (removal efficiencies of NH4+-N and TN were as high as 88.43% and 86.09%, respectively) and biofilm formation (total organic carbon, protein, polysaccharide and biofilm quality increased by 8.9 mg/L, 35.5 mg/L, 0.21 mg/L and 38.4 mg/L, respectively) of wetland systems. Zobellella, Achromobacter, and other HN-AD bacteria were enriched in the 5–20 cm zone. These results indicated that QS facilitated bacterial growth, denitrification, and biofilm formation of HN-AD bacteria, which is of great significance for the purification of nitrogen-polluted wetlands in coastal areas.