土壤反硝化对磺胺嘧啶及抗性基因消减的影响

摘要

Mixed contamination with antibiotics and antibiotic resistance genes (ARGs) in farmland soil has become an emerging threat against human health and environmental security. However, little attention has been paid on the impact of anoxic denitrification on the dissipation of soil antibiotics and ARGs. Therefore, the present work collected the subsurface mixed-contaminated arable soil around dairy farm, and investigated the influence of denitrification process on the dissipation of soil sulfonamides and their correlated ARGs. The results indicated that nitrate addition to the soil clearly improved the nitrate transforming rate in both soil and water phases, the N2O production, and the dissipation of soil sulfonamides and ARG abundance. In addition, the clearly negative correlation between the abundance denitrifying genes (nirK,nirS, andnosZ) and sulfonamide resistance genes (sulI andsulII) demonstrated that more sufficient the nitrate nitrogen, the stronger the express of denitrifying genes and the stronger the denitrification process; in order to promote the sulfonamide/ARG dissipation. Moreover, through high-throughput sequencing and the experiment of the separation of denitrifying bacteria,Proteobacteria Lysinibacilluswere the predominant strains isolated from anoxic soil among various treatments, which likely played an important role in prompting denitrifying procedure and stimulating sulfonamide/ARG dissipation. This work provided novel information on the anoxic dissipation of soil antibiotics and the ARG proliferation.%农田土壤中抗生素及抗性基因的复合污染已给生态环境安全和人体健康带来了全新隐患.针对厌氧条件下,反硝化作用过程对土壤抗生素乃至抗性基因消减影响的研究一直相对较少.因而,本研究采集牛粪堆积池塘周边底层农田土壤作为目标污染土壤,重点研究反硝化作用过程对土壤磺胺嘧啶及抗性基因消减动态的影响.结果表明:相较于原始污染土壤处理(T1),添加了NO–3-N的处理(T2)可以显著强化土壤和水相中反硝化速率,提升N2O的产气速率,促进土壤中磺胺嘧啶浓度和抗性基因丰度的快速降低;同时发现土壤反硝化基因(nirK、nirS和nosZ)与磺胺类抗性基因(sulI和sulII)呈显著负相关(P<0.05),说明当NO–3-N底物越充足,土壤反硝化细菌活性往往被激活,其反硝化功能基因表达就越活跃,土壤反硝化作用过程就越强烈,从而反馈作用促进磺胺嘧啶抗生素的厌氧消减,进而有助于sul系列抗性基因丰度的显著衰减;同时通过高通量测序技术及对反硝化细菌的分离筛选后,发现变形菌门(Proteobacteria)赖氨酸芽胞杆菌属(Lysinibacillus)的细菌是土壤厌氧反应前后的主导优势菌群,对于强化反硝化过程和促进磺胺嘧啶及sul抗性基因的消减发挥了潜在的积极作用.本研究结果可为探明土壤中抗生素的厌氧消减过程和缓解抗性基因的扩散传播提供新颖的认知基础.