The Mechanism Research Of Earthworm Promoting The Degradation Of Residual Tetracycline In Soil

Misuse of tetracycline will cause tetracycline to be released into the environment.Because tetracycline is chemically stable,it can remain in the soil for a long time,which will harm ecological safety and human health.Earthworms are common organisms in the soil,and their activities and secretions can repair contaminated soil.In this study,tetracycline,earthworms and soil were used as the research objects.Through the microcosm indoor culture experiment method,two ecological types of earthworms,E.wilhelminii and Eisenia vulgaris,were selected to study the physical and chemical properties of soil,earthworm enzyme activity,soil microbial community structure,and Changes in tetracycline resistance genes,to explore the mechanism of earthworms promoting the degradation of residual tetracycline in the soil The main findings are as follows:(1)The addition of earthworms can promote the degradation of residual tetracycline in the soil,and the degradation effect of Pheretima guillemi is better than that of Eisenia foetida The degradation rates of soil treated with low concentration and high concentration of tetracycline after standing for 28 days were 50.33%and 56.27%,respectively.The degradation effect of Eisenia foetida on soil tetracycline was increased by 28.04%and 16.65%,and the degradation of soil tetracycline by Eisenia foetida.The effect was increased by 21.07%and 10.82%respectively.(2)Tetracycline will affect the physical and chemical properties of the soil,and the addition of earthworms can improve the soil environment.Tetracycline will lower the pH of the soil and significantly reduce the content of soil nitrate nitrogen,available potassium and available phosphorus at high concentrations.Earthworms significantly lower soil pH and increase soil electrical conductivity,Pheretima guillemi significantly increased the content of nitrate nitrogen and available phosphorus,and Eisenia foetida significantly increased the content of ammonium nitrogen and nitrate nitrogen.Under tetracycline pollution,the addition of earthworms can adjust soil pH and conductivity to improve their own living environment.The addition of Pheretima guillemi can significantly increase the content of soil nitrate nitrogen and available phosphorus.However,the content of nitrogen in the soil significantly reduces the content of available phosphorus,and the content of soil nitrate nitrogen,available potassium and available phosphorus is significantly increased at high concentrations.Earthworms can promote the degradation of tetracycline in the soil by increasing the content of soil EC,nitrate nitrogen and available phosphorus.Tetracycline and earthworms have a significant effect on soil enzyme activity.Tetracycline can inhibit soil urease activity and enhance cellulase activity.In high concentrations,it inhibits peroxidase activity.Earthworms can reduce soil urease activity and increase cellulase activity;in tetracycline soils Among them,the addition of E.wilhelminii can reduce the activities of soil urease and lignin,the addition of Eisenia vulgaris can reduce the activities of soil urease and peroxidase,and the activity of soil ligninase at high concentrations(3)The biomass of earthworms decreased significantly after 28 days,and the stress response of Pheretima guillemi and Eisenia foetida to tetracycline stress was different.At low concentrations,the SP content,T-AOC,AchE activity,SOD activity,and GST activity in the body of Eisenia foetida The content,POD activity and GST activity decreased significantly.At high concentrations,T-AOC,MDA,AchE activity,GST activity and CL activity were significantly reduced in the body of Eisenia foetida,SP content,SOD activity and POD activity were significantly increased;SP content,T-AOC,SOD activity and CL activity increased significantly,and MDA content,POD activity and GST activity decreased significantly.The POD activity in earthworms was significantly positively correlated with the degradation of tetracycline in the soil.(4)Tetracycline in the soil has no significant effect on the diversity of the microbial community structure and the abundance of dominant species at the genus level,but the addition of Pheretima guillemi significantly changed the structure of the soil microbial community,and in the soil contaminated by tetracycline,Pheretima guillemi The microbial community was significantly changed,and the soil microbial structure in the high tetracycline concentration treatment could be distinguished from the original soil area.Pheretima guillemi increases the abundance of Nocardioides,Sphingomonas,Aeromonas,and Flavobacterium;in tetracycline-contaminated soil Under the conditions,the addition of Pheretima guillemi increased the abundance of Nocardioides,Aeromonas and Flavobacterium,all of which were significantly positively correlated with the degradation rate of tetracycline in the soil.There was a significant negative correlation between SP and Hyphomicrobium,AchE and Nitrospira,POD and Marmoricola,and a positive correlation between T-AOC and Pseudomonas,AchE and Marmoricola,AchE and Pseudomonium,CL and Pseudomonium.Nitrospira,Marmoricola and Pseudomonas are related to the degradation of tetracycline.(5)The 60 tetracycline resistance genes screened out in the soil cover three functional groups of tetracycline resistance gene efflux pump protein,tetracycline resistance gene ribosomal protective protein and tetracycline deconstruction enzyme.Pheretima guillemi can affect the distribution of tetracycline resistance genes.Soil pH,EC,available phosphorus,and nitrate nitrogen play an important role in the formation of tetracycline resistance genes.Among the 12 tetracycline deconstruction enzymes,tetracycline and Pheretima guillemi can stimulate the soil to produce Tet(X3).Low concentrations of tetracycline significantly increase the gene abundance of tet(49),and Pheretima guillemi significantly increase the gene abundance of tet(50).At low concentrations,the addition of Pheretima guillemi significantly increased the gene abundance of Tet(X4),and at high concentrations significantly increased the gene abundance of tet(50)and tetX,of which tetX generally exists in Aeromonas and so on in the microorganisms.