Community Structure And Denitrification Characteristics Of Aerobic Denitrifiers In Lake And Reservoir

Aerobic denitrifiers,aerobic denitrifying bacteria and aerobic denitrifying fungi,enriched by intermittent aeration,screened with screening culture media and treated by ultrasonic wave,were isolated and screened from the sediments of Jin pen reservoir,Xingqing Park and Changle park.Denitrification characteristics and community composition of aerobic denitrifiers,denitrification characteristics of the strain KK99and the expression level of narG,nirS and nosZ functional genes in aerobic/anaerobic condition and isolation and characterization of a novel aerobic denitrifying fungi were investigated.At the same time,six urban lake landscape water bodies were selected to explore the relationship between the water quality and the nirS-Type denitrifier community structure and diversity with Illumina high-throughput sequencing technique.?1?The three groups of aerobic denitrifier communities H-30,X-10 and C-30were successfully screened out and their aerobic denitrification capability was studied.The results showed that the three groups of aerobic denitrifier communities had high efficiency of denitrification.After 24h,the total nitrogen?TN?removal rate of aerobic denitrifier communities H-30,X-10,and C-30 achieved 83.04%,83.40%and 82.68%,respectively.There was only a small amount of nitrite?NO₂^--N?was accumulated.Illumina MiSeq high-throughput DNA sequencing illustrated three groups of nirS-Type aerobic denitrifier communities structure compositions were significantly different.The dominant strains of aerobic denitrifier communities H-30,X-10 and C-30 were Bacillus subtilis,Paracoccus pantotrophus and Pseudomonas stutzeri,respectively.Among them,P.stutzeri existed in three groups of aerobic denitrifier communities,and the proportion of H-30 and X-10 was almost the same.while P.xiamenensis existed only in the aerobic denitrifier communities H-30.?2?The strain KK99 can perform denitrification under aerobic/anaerobic conditions,and have high efficiency of denitrification under two different conditions.The expression level of functional genes narG is relatively low,so it plays a relatively small role in gene expression level.The expression level of nirS and nosZ genes was relatively high,but there was a significant difference between them.Under anaerobic pathway,nirS gene plays a vital role and nos Z gene plays a vital role in aerobic pathway.The detection of functional genes explains why denitrification can be carried out under aerobic and anaerobic conditions.At the same time,the strain KK99 also has the capability of simultaneous nitrification and denitrification.Under aerobic condition,the nitrate and ammonia can be removed simultaneously.At 24h,the removal rate of total nitrogen?TN?is 76%.?3?A fungal strain KPL108 with an outstanding capacity of aerobic simultaneous nitrifying-denitrifying was isolated from a drinking water reservoir located in Shaanxi province,China.The strain was identified as Hanseniaspora uvarum KPL108 by morphological features and molecular techniques.This strain is capable of removing nitrate and ammonia simultaneously.In the denitrification system with nitrate as sole nitrogen,the nitrate removal efficiency could reach upto 97%after 25h,without nitrite accumulation.Nitrogen balance analysis of denitrification exhibited that approximately92%of the initial nitrogen was removed as gas products.Response surface methodology?RSM?experiments revealed that the maximum removal of total nitrogen?TN?occurred under the following conditions:C/N ratio of 6.42,shaking speed of 109.68r/min,temperature of 28.48 ^oC and initial pH of 8.15.The effect of the initial pH and temperature on the removal of total nitrogen is the greatest.The results reveal that the strain KPL108 can be used for bioremediation of micro-pollutants present in drinking water reservoirs.?4?In six urban lake landscape water bodies,the water body of Yongyang Park?YY?was belonged to IV water quality,Qujiang Park?QJ?,Mutasi Park?MTS?and Xinjiyuan Park?XJY?water bodies were belonged to?water quality,and Fengqing Park?FQ?and Laodong Park?LD?water bodies belonged to inferior V water quality.High throughput sequencing results revealed that there were significant differences in the nirS-Type denitrifier community composition among six urban lake landscape water bodies.The most dominated genus species in FQ and LD is Paracoccus sp.;The most dominated genus species in QJ and YY is Pseudomonas sp.;The most dominated genus species in MTS and XJY is Rubrivivax sp..Principle component analyses?PCA?showed that nirS-Type denitrifier communities of XJY and MTS were mainly regulated by NH₄⁺-N and COD_Mn,LD and FQ were significantly influenced by NO₃^--N,NO₂^--N,TN,TP,DO?Monte Carlo permutation,P<0.05?and YY were significantly influenced by pH value?Monte Carlo permutation,P<0.05?.Our results indicated that nirS-Type denitrifier communities were regulated by different water quality indicators.