Insight Into Quorum Sensing And Microbial Community Of An Anammox Consortium In Respond To Salt Stress

Anaerobic ammonia oxidation(anammox)process has been a cost-effective and environmentally friendly nitrogen removal process recently.Most nitrogen-rich wastewaters also contain high salinity which is a limiting factor for wastewater treatment.High salinity can induce cell plasmolysis due to rapid increase in osmotic pressure.Due to anammox granular is sensitive to various salinities,a sequential batch reactor was operated to construct an anammox system in this study.The nitrogen removal performance,quorum sensing(QS)and microbial community of anammox granular were investigated under different salinities.The following results were obtained:Based on these results,anammox granular in this reactor could gradually adapt to a salinity of 12 g NaCl/L but substantially inhibited by 18 g NaCl/L.the anammox granular activity was affected slightly at a salinity of 5 g NaCl/L.When the salinity increased from 5 to 12 g NaCl/L,the nitrogen removal performance of anammox granular was significantly inhibited and then recovered after a period of acclimation.When the salinity was further increased to 18 g NaCl/L,the performance of anammox granular decreased sharply,which indicated that anammox granular could not adapt to 18 g NaCl/L.3OC6-HSL-mediated QS was investigated under different salinities shock.The results showed that when subjected to the salt stress,QS of anammox granular would be activated.When the salinity sharply increased to 10 g NaCl/L,the concentration of 3OC6-HSL rapidly increased,and then decreased,showing a closely correlation with salinity.Then,as the salinity gradually increased,the concentration of 3OC6-HSL also increased rapidly.When the salinity increased to 18 g NaCl/L,the cell death of Candidatus Brocadia sinica induced by salinity,resulting in a rapid decrease in the concentration of 3OC6-HSL.The shifts of microbial community in the reactor under the salt stress were investigated.The results showed that after the long-term exposure to salt stress,the diversity of the microbial community would decline with the increased salinities,while increased after adapting to salinity.The anammox bacteria Candidatus Brocadia sinica detected in the system suddenly dropped to 14.4% when the salinity increased to 10 g NaCl / L.This may be the main reason for Planctomycetes decreased from the 10.7% range to 5.5%.Due to the acclimation to the gradual increase of the salinity(7-12 g NaCl / L),the abundance of Candidatus Brocadia sinica gradually recovered.However,when the salinity increased to 18 g NaCl / L,the abundance of Candidatus Brocadia sinica sharply decreased,and the marine anaerobic ammonia-oxidizing genus Candidatus scalindua appeared,indicating a major shift in the anammox community in response to the salt stress.