降解菌和植物对土霉素污染盐渍化土壤的修复

Remediation of Oxytetracycline-contaminated Salinized Soil by Oxytetracycline-degrading Bacteria and Plants

摘要:

畜禽粪污是抗生素和抗生素抗性基因（Antibiotic resistance genes，ARGs）的重要储存库，而施用有机肥是改良盐渍化土壤的有效途径之一，因此改良过程中土壤存在被抗生素污染的风险。土霉素是畜禽粪污中常见且含量较高的抗生素，本文利用盆栽试验研究了土霉素污染盐渍化土壤的微生物和植物修复效果。结果表明，与原始土壤+土霉素（CK）相比，试验30d时单独接种降解菌（Inoculation bacteria，IB）、单独种植生菜（Growing lettuce，GL）及降解菌和生菜联合修复（Bacterial lettuce combined，BLC）土壤中土霉素含量分别降低42.47%、39.01%和40.44%；单独接种降解菌DB1时降解率最高，达54.93%。与CK处理相比，IB、GL和BLC处理普遍降低了土壤ARGs总相对丰度，30d时降幅分别为53.84%~73.86%、63.64%和64.17%~76.47%，主要以降低喹诺酮类（qepA、oqxB和qnrB等）和四环素类ARGs（tetPB-01、tetPB-05和tetR-02等）为主。3种修复方式改变了土壤细菌多样性。30d时，IB、GL和BLC处理均降低了Actinobacteriota相对丰度，属水平上明显增加了Woeseia数量，降低了Luteimonas数量。3种修复方式增加了个别基因（如tetX、tetG-01、ermF等）水平转移风险。整体来讲，单独接种降解菌、单独种植生菜及降解菌和生菜联合修复均能降低盐渍化土壤中土霉素含量，且对ARGs的产生具有明显抑制作用；但单纯植物降解对土霉素污染的盐渍化土壤修复能力有限，接种高效降解菌修复效果最佳；单独接种降解菌主要通过影响土壤微生物群落多样性及结构和抑制可移动元件（Mobile genetic elements，MGEs）水平基因转移来减弱ARGs传播；联合修复则主要通过降低微生物群落多样性、改变其结构而降低ARGs丰度。研究结果可为减弱ARGs在盐渍化土壤-植物生态系统中的传播提供科学依据。

Abstract:

Livestock manure is an important reservoir of antibiotics and antibiotic resistance genes (ARGs), and the application of organic fertilizer is one of the effective ways to improve salinized soil. Therefore, salinized soil has the risk of being contaminated by antibiotics. Oxytetracycline is a common and high content antibiotic in livestock and poultry manure. The microbial and phytoremediation effects of salinized soil contaminated by oxytetracycline were studied by pot experiment. The results showed that compared with the original soil + oxytetracycline (CK), the contents of oxytetracycline in the soil inoculated with degrading bacteria (inoculation bacteria, IB) alone, lettuce (growing lettuce, GL) alone and combined remediation of degrading bacteria and lettuce (BLC) were decreased by 42.47%, 39.01% and 40.44% at 30d, respectively. The degradation rate was the highest when DB1 was inoculated alone, reaching 54.93%. Compared with CK treatment, IB, GL and BLC treatments generally significantly reduced the total relative abundance of ARGs in soil by 53.84%~73.86%, 63.64% and 64.17%~76.47% at 30d, respectively, mainly by reducing quinolones (qepA, oqxB and qnrB, etc. ) and tetracycline ARGs (tetPB-01, tetPB-05 and tetR-02, etc.). Three ways changed the diversity of soil bacteria. At 30d, IB, GL and BLC decreased the relative abundance of Actinobacteriota, significantly increased the number of Woeseia and decreased the number of Luteimonas at the genus level. The three repair methods increased the risk of horizontal transfer of individual genes (such as tetX, tetG-01 and ermF). Overall, single inoculation of degrading bacteria, single planting of lettuce and combined remediation of degrading bacteria and lettuce can reduce the content of oxytetracycline in salinized soil, which had a significant inhibitory effect on the production of ARGs;however, the remediation ability of pure plant degradation to oxytetracycline-contaminated saline soil was limited, and the remediation effect of inoculation with highly efficient degrading bacteria was the best. Inoculation of degrading bacteria alone reduced the spread of ARGs mainly by affecting the diversity and structure of soil microbial communities and inhibiting the horizontal gene transfer of mobile genetic elements (MGEs). Combined remediation mainly reduced the abundance of ARGs by reducing the diversity of microbial communities and changing their structure. The results aimed to provide a scientific basis for reducing the spread of ARGs in salinized soil-plant ecosystems.