Effect Of Zobellella Sp.Strain On Microbial Nitrogen Removal Pathways In Kandeliaobovata Constructed Wetland

Constructed wetland is an ecological sewage treatment technology.Microbial denitrification is the most important pathway of nitrogen removal in constructed wetlands.In this experiment,a salt-tolerant and enriched culture of denitrifying bacteria was used to denitrify the substrate of the constructed wetland.Finally,an indigenous salt-tolerant and aerobic denitrifying strain,A63,was isolated and purified.It was initially identified as Zobellella sp.by 16S rDNA sequence analysis,In this experiment,two different types of Kandelia obovataconstructed wetland test systems were built,and the strain A63 was added to the artificial wetland water for biological enhancement treatment.The effect of strain A63 on the denitrification mechanism of different types of constructed wetlands was explored to show various forms of nitrogen.In the vertical flow pattern of vertical flow constructed wetland systems,qPCR techniques were used to detect the gene abundances of 16S r DNA,amoA-AOA,amoA-AOB,nirS,and nirK in each stroma of different systems,reflecting total bacteria,AOA,AOB,and the main results of the two types of denitrifying bacterial abundance are as follows:?1?The constructed wetland test system with high removal efficiency of total nitrogen was successfully constructed in this test.The removal rate of total nitrogen was only 52.7%in the artificial wetland test system A without added bacteria,while the strain A63 was added.The total nitrogen removal rates of the constructed wetland test systems B and C were 68.6%and 70.0%,respectively,indicating that the addition of strain A63 enhances the system's efficiency in removing total nitrogen,especially improvethe removal efficiency of nitrate.?2?In the vertical flow constructed wetland test system,although the addition of strain A63 enhances the system's removal efficiency of total nitrogen,the system with strain A63 represents that the 16S rDNA gene of the total bacteria is less than the artificial wetland without strains the system shows that the addition of strain A63 is beneficial to increase the denitrification efficiency of microorganisms in the system and increase the proportion of denitrifying microorganisms.In each small-scale system,the abundance of strain amoA-AOA was much higher than that of amoA-AOB,indicating that under a salinity stress condition,AOB-mediated aerobic ammoxidation pathways were inhibited,whereas AOA-mediated pathway is the main ammoxidation pathway in this pilot system.?3?Although the nitrite reductase synthesizing gene of strain A63 was nir K,the results of the determination of two different types of nitrite reductase functional genes ofnirS and nirK showed that the nirS gene in each wetland system was of therange of10¹⁰to 10¹¹.Copies/g,andnirK was 10⁸ to 10¹⁰ copies/g,and the copy number of the nirS gene was much higher than that of the nirK gene.The results showed that strain A63 enhanced the denitrification efficiency of Kandelia obovata wetland.At the same time,the enhanced experiment did not have a significant impact on the type of denitrifying microorganisms in the wetland substrate.