The Responses Of Ammonia Oxidizing Microorganisms To Soil Cu And Antibiotics Stress

In this study,brown soil,desert soil,black soil,paddy and Wu Tu soil are selected as the tested soils to investigate the impact of different concentrations with Cu and sulfadiazine（SDZ）on the potential nitrification rate（PNR）of soils.Besides,the fluorescence quantitative PCR,Miseq sequencing and other molecular biology techniques are used to study the ammonia oxidizing microorganisms（AOA and AOB）response under the stress of specific pollutant concentrations in brown soil,black and desert soil on the basis of the PNR results.The main achievements of this paper are as follow:1.The impact of Cu and SDZ on soil PNR（1）The PNR values of 5 tested soils decrease gradually with the increase of Cu,and the EC₂₀values of brown soil,black soil,desert soil,paddy and Wu Tu soil are 181.82、161.20、156.63、1110.07 and 305.86 mg·kg^-1.According to the risk screening values of Cu in GB15618-2018(50-200 mg·kg^-1),we find that brown soil,black and desert soil PNR are sensitive to Cu stress,which could be used to evaluate the ecological risk with soil Cu pollution.（2）A good dose-response curves of SDZ and soil PNR are just found for desert,brown and Wu Tu soil,with the EC₂₀values of 6.87、4.14 and 4.44 mg·kg^-1.Soil PNR can’t be used to evaluate the ecological risk with soil SDZ pollution compared with their environmental concentration(1.93-760.09μg·kg^-1).（3）For the combined pollution of Cu and SDZ,we find that the interaction types of Cu and SDZ are antagonistic in brown soil based on the inhibition rate of PNR,while the synergistic effects are dominant in black and paddy soil.As for desert and black soil,their interaction types are related to the concentrations of two pollutants.（4）Pearson correlation analysis is used to explore the relationship between various indexes.The results show that soil p H is significantly correlated with PNR₀（R²=0.58,p<0.05）and EC₅₀（Cu）（R²=0.65,p<0.05）,which is the main environmental factor affecting soil PNR.2.The responses of AOA and AOB for the stress of Cu and SDZ（1）The abundance analysis of ammonia oxidizing microorganisms in the tested soils shows that AOA is dominant in black soil,while AOB is dominant in brown and desert soil.The abundance of ammonia oxidizing microorganisms is sensitive to the single and combined stress of Cu and SDZ in brown soil,but not in desert soil.In black soil,ammonia oxidizing microorganisms abundance has resistance under all treatments except the SDZ single pollution.As for the diversities of amo A-AOA and AOB,Cu reduce their diversity in brown and desert soil,but increase other soils’diversities slightly.The diversities of ammonia oxidizing microorganisms increase in both black and brown soil under SDZ single pollution,except in desert soil.Besides,the diversities of amo A-AOA and AOB in brown soil and amo A-AOB in black soil increase when add two pollutants,while the diversities of amo A-AOA and AOB in desert soils and amo A-AOA in black soil decrease.Furthermore,except the interaction types of Cu and SDZ on amo A-AOA and AOB in brown soil are antagonistic,others are synergistic.（2）Under the single and combined pollution stress of Cu and SDZ,the abundance change of ammonia oxidizing microorganisms in brown and black soil is consistent with the trend of PNR,indicating the Cu and SDZ change soil PNR by affecting the ammonia oxidizing microorganisms.For desert soil,Cu and SDZ increase the abundance of ammonia oxidizing microorganisms（different from the PNR response）,but their dominant population Nitrosospira and Nitrosovibrio are reduced.So,Cu and SDZ reduce desert soil PNR by inhibiting Nitrosospira and Nitrosovibrio activity.The linear regression and redundancy analysis show the response of soil ammonia oxidizing microorganisms to Cu and SDZ single and combined pollution are greatly affected by soil PNR₀,p H,clay content or other factors.There,Nitrososphaera is mainly affected by p H,Cu,Clay and SDZ.Nitrosospira is sensitive to Cu and SDZ and Nitrosovibrio is influenced by the CEC of soil.In this study,soil nitrification is analyzed by combining with ammonia oxidizing microorganisms to explore the influence mechanism of Cu and SDZ on ammonia oxidizing microorganisms.At the same time,the interaction types of soil PNR and ammonia oxidizing microorganisms under combined pollution of two pollutants and the correlation between them and environmental factors are analyzed,which has profound significance for the establishment of biological evaluation methods and remediation techniques for soil contaminated by heavy metals and antibiotics.