Microcystins (MCs) pose a significant threat to human health and the environment due to their persistence and toxicity as potent cyanobacterial toxins. Effective biodegradation strategies are required for their removal and detoxification. In this study, bacterioplankton were isolated from eutrophic reservoir water used for crop irrigation and tested for their ability to degrade MCs. These bacteria are hydrologically transported from the contaminated reservoir to downstream farms where they are able to grow under the favorable conditions provided by a multi-soil-layering (MSL) system, a low-cost and locally applicable ecotechnology for the removal and detoxification of MCs. These bacteria enhance the ability of the MSL to remove MCs by forming biofilms within the MSL system. The bacterial strains were then sequenced and their partial 16S rRNA was compared to the reference strains in the NCBI database. The effectiveness of the MSL system in the removal of MCs from water was evaluated. The MSL utilizes a layered soil matrix that promotes microbial growth and physicochemical interactions that enable the removal of various contaminants. The mechanisms of MC removal in the MSL were evaluated by studying the physicochemical properties of the system substrate before and after treatment using X-ray fluorescence, zeta potential, and scanning electron microscopy (SEM) analyses. The microbial functional groups, including ammonifying and denitrifying bacteria, were also investigated in the MSL soil matrices before and after treatment. The results showed that seven bacterial strains exhibited high MC degradation capabilities, with MC degradation performance exceeding 97%. These isolated bacterial strains had a nucleotide identity score of 100% and an E value of 0.0 compared to reference strains. The MSL showed a 99% removal rate for MC-LR and MC-YR, as well as significant reductions in other pollutants, including COD (60%), BOD5 (60%), chlorophyll-a (96%), pheophytin (70%), organic nitrogen (80%), and nitrites (90%). After treatment, there was a statistically significant increase in the total bacterial count, as well as ammonifying and denitrifying bacteria, in the MSL soil matrices compared to their state before treatment. SEM analyses revealed the formation of dense biofilm microbiota, indicating additional biological processes besides adsorption for MC reduction. Overall, the MSL provides a low-cost alternative for the removal of MCs and cyanobacteria with minimal resource requirements and maintenance. It offers a promising solution for mitigating toxic cyanobacterial blooms, ensuring safe agricultural water reuse.

中文翻译：

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去除微囊藻毒素的创新方法：浮游细菌生物降解和多层土壤系统性能评估

微囊藻毒素（MC）因其作为强效蓝藻毒素的持久性和毒性而对人类健康和环境构成重大威胁。需要有效的生物降解策略来去除和解毒。在这项研究中，从用于农作物灌溉的富营养化水库水中分离出浮游细菌，并测试了它们降解 MC 的能力。这些细菌通过水文从受污染的水库输送到下游农场，在那里它们能够在多层土壤分层（MSL）系统提供的有利条件下生长，这是一种低成本且适合当地适用的生态技术，用于去除和解毒MCs 。这些细菌通过在 MSL 系统内形成生物膜来增强 MSL 去除 MC 的能力。然后对细菌菌株进行测序，并将其部分 16S rRNA 与 NCBI 数据库中的参考菌株进行比较。评估了 MSL 系统去除水中 MC 的有效性。 MSL 利用分层土壤基质促进微生物生长和物理化学相互作用，从而去除各种污染物。通过使用 X 射线荧光、zeta 电位和扫描电子显微镜 (SEM) 分析研究处理前后系统基材的物理化学性质，评估了 MSL 中 MC 去除的机制。还对处理前后 MSL 土壤基质中的微生物功能群（包括氨化细菌和反硝化细菌）进行了研究。结果表明，7株菌株表现出较高的MC降解能力，MC降解性能超过97%。与参考菌株相比，这些分离的细菌菌株的核苷酸同一性得分为 100%，E 值为 0.0。 MSL 显示 MC-LR 和 MC-YR 的去除率为 99%，其他污染物也显着降低，包括 COD (60%)、BOD5 (60%)、叶绿素-a (96%)、脱镁叶绿素 (70 %）、有机氮（80%）和亚硝酸盐（90%）。处理后，与处理前的状态相比，MSL 土壤基质中的细菌总数以及氨化细菌和反硝化细菌数量有统计学上的显着增加。 SEM 分析揭示了致密生物膜微生物群的形成，表明除了吸附以减少 MC 之外还存在其他生物过程。总体而言，MSL 为去除 MC 和蓝藻提供了一种低成本的替代方案，且资源需求和维护最少。它为减少有毒蓝藻水华、确保农业用水的安全再利用提供了一种有前途的解决方案。