Assessing the efficiency and the side effects of atrazine-degrading biocomposites amended to contaminated soil

Even decades after being banned in Europe, atrazine can still be found in soils. Bioaugmentation with pesticide-degrading bacteria is a remediation technique that is already used experimentally to reclaim polluted soils. Its efficiency still needs to be improved and the use of carrier materials to deliver and stabilize pesticide-degrading microbes could be an interesting way to in situ investigations. Here, we produced atrazine-degrading biocomposites by bacterial biofilms either a single strain or a four-species consortium grown on zeolite as the carrier material. We evaluated their efficiency in mineralizing 14C-atrazine of agricultural soil versus free-living cells in a microcosm experiment. We also assessed the side effects of this bioremediation technology on the autochthonous soil microbial community. We showed that the atrazine mineralization potential of the free-living cells was higher than that of the biocomposites. However, soil microcosms inoculated with the biocomposites displayed significantly higher atrazine mineralization potential than the ones inoculated with free-living cells. Also, higher stability of the biocomposites after 15 and 34 days of incubation was confirmed by qPCR of the atrazine-degrading genes. The results of 16S rRNA amplicon sequencing indicated that the side effects of biocomposites on the autochthonous microbial diversity and composition are mild and depend on the atrazine substrate and zeolite. Altogether, our results provide the first evaluation of the efficiency and the ecotoxicological impacts of atrazine-degrading biocomposites in the soil.

即便在欧洲被禁用数十年后，莠去津（atrazine）仍可在土壤中被检出。利用降解农药的细菌开展生物强化（bioaugmentation）是一项已在实验阶段应用的污染土壤修复技术，但其修复效率仍有待提升；而借助载体材料递送并稳定降解农药的微生物，或是颇具潜力的原位研究方向。
本研究以沸石作为载体材料，利用单菌株或四菌株联合体形成的细菌生物膜，制备了可降解莠去津的生物复合材料。通过微宇宙实验，我们评估了该生物复合材料与游离态细胞分别对农业土壤中¹⁴C-莠去津的矿化效率。同时，我们也考察了该生物修复技术对土壤土著微生物群落的潜在副作用。
研究结果显示，游离态细胞的莠去津矿化潜力高于生物复合材料。然而，接种生物复合材料的土壤微宇宙，其莠去津矿化潜力显著高于接种游离态细胞的微宇宙体系。此外，通过对莠去津降解基因的实时定量聚合酶链式反应（qPCR）检测，证实了生物复合材料在培养15天与34天后仍具有较高稳定性。
16S rRNA扩增子测序结果表明，生物复合材料对土著微生物多样性与群落组成的副作用较为温和，且其影响程度取决于莠去津底物与沸石的共同作用。综上，本研究首次评估了降解莠去津的生物复合材料在土壤中的修复效率与生态毒理学影响。