Degradation Characteristics Of Atrazine-degrading Strain ZF1 And Its Bioremediation Ability To Contaminated Soil

Over the past 40 years,atrazine has been widely used around the world in the control of broad-leaved weeds growing in the fields of corn,wheat,sorghum and other crops.However,due the long half-life,easy diffusion,and high mobility of atrazine,its long-term use will pose a huge threat to the ecological environment and human health.Microbial degradation is an effective method to rapidly remove atrazine to keep the environment safe.In this study,a high-efficiency atrazine-degrading bacterium was isolated from atrazine-contaminated soil,and its degradation characteristics and degradation pathway were studied.In addition,the ability of this degrading bacterium to remediate atrazine-contaminated soil was further studied,and the effects of the strain on soil enzymes and soil microbial community were also explored.A bacterium ZF1,which can efficiently degrade atrazine,was isolated from the wheat field soil in Henan Province through enrichment culture in this study.The strain can grow with atrazine as carbon and nitrogen sources.Phenotypic characterization and 16 S r DNA sequencing indicated that the isolate strain belonged to the Paenarthrobacter ureafaciens.The results of single-factor test showed that the growth and atrazine-degradation efficiency of strain ZF1 were in a broad ranges of temperature(5～50℃)and p H(5.0～11.0),and it could tolerate at least 1500 mg/L of atrazine.The optimum carbon source of this strain was starch,and the additional nitrogen source could promote the degradation of atrazine.The optimal culture conditions for atrazine degradation by strain ZF1 were obtained by response surface optimization method: temperature of 31.33℃,p H of 7.7,and inoculum volume of 5.27%.Under the optimal experimental conditions,the degradation rate of atrazine could reach 80 mg/L/hr when starch was used as carbon source.Gene identification analysis revealed that ZF1 contained the genes trz N,atz B,and atz C,which could transform atrazine into cyanuric acid.It is speculated that the degradation pathway was atrazine–hydroxyatrazine–N-isopropylammelide–cyanuric acid.The results of enzyme localization showed that the degradation enzyme secreted by strain ZF1 belonged to intracellular enzyme.The degradation ability of Paenarthrobacter ureafaciens ZF1 on atrazine in soil was examined by micro-remediation experiments,and its effects on soil enzymes and soil bacterial communities were evaluated.The results showed that strain ZF1 accelerated the degradation of atrazine and could remove 99.3% of atrazine(100 mg/kg soil)within 6 days.During soil bioremediation,atrazine promoted the activities of urease and cellulase,and inhibited the activities of sucrase and catalase,while the strain ZF1 significantly promoted the activities of these four enzymes.High-throughput sequencing of 16 S r RNA genes showed that ZF1 affected the relative abundance and community structure of bacterial,and promoted the diversity and evenness of microbial communities.Furthermore,redundancy analysis revealed a certain correlation among the strain ZF1,atrazine residue,soil enzyme activity,and soil bacterial community,indicating that the soil environment and microorganisms interacted with each other.Overall,the discovery of strain ZF1 enriched the resources of atrazine-degrading strains,and its excellent biodegradation ability and ecological restoration ability indicated that it has great potential for application in the bioremediation of atrazine-contaminated sites in the future.