Microcystin-LR (MC-LR), released by algal bloom, poses severe threats to human beings and ecosystem because of its high persistence and toxicity. Due to anammox bacteria’s vulnerability to adverse environmental factors, and the impact of MC-LR on anammox should not be overlooked. In this work, the response mechanism of anammox to MC-LR was dissected from macroscopic to microscopic level. Spectroscopy and rheological tools demonstrated that hydrogen bond force provided by extracellular polymeric substances (EPS) and relatively stable yield stress of sludge endowed anammox granules with ability to resist in deformation for maintaining nitrogen metabolism. Anammox process can adaptively against MC-LR at biology level. At 1 mg/L MC-LR, the relative abundance of functional microorganism (Candidatus Brocadia and Candidatus Kuenenia) and core gene (hzs and hdh) were increased for self-maintenance, while the abundance of denitrifying bacteria was increased by 7.72% at 3 mg/L MC-LR to prevent further collapse of nitrogen metabolism. Notably, high concentration of MC-LR with degradation-resistant property would penetrate EPS barrier to disturb intracellular anti-oxidation balance and attack respiratory chain, thus directly disrupting nitrogen transformation and electron transfer, which led to a 25.6% decrease in the nitrogen removal efficiency. Computational chemistry further demonstrated that MC-LR conjugated intracellular biomolecules to affect the biological functions. This work provides the insights into the fate and risk of MC-LR in anammox.

Environmental Implication

High persistence, anti-oxidation and biotoxicity of MC-LR seriously threatened the human health and aquatic system. In this work, the response mechanism of anammox to MC-LR was overall dissected. Hydrogen bond force, increased sludge yield stress and adaptive regulation mechanism of anammox converts to denitrification endowed anammox bacteria with ability to resist deformation. However, MC-LR is degradation-resistant and it disturbed intracellular anti-oxidation balance, attacked respiratory chain and conjugated intracellular biomolecules to affect anammox functions. This study shed the light on the fate of MC-LR in anammox and inspire increasing focus on how other biological wastewater treatment processes response to MC-LR disturbance.

中文翻译：

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从颗粒特性、细胞内代谢和分子对接的角度破译厌氧氨氧化反应与微囊藻毒素的隐藏防御行为和结合机制

藻华释放的微囊藻毒素-LR （MC-LR） 因其高持久性和毒性而对人类和生态系统构成严重威胁。由于厌氧氨氧化菌易受不利环境因素的影响，MC-LR 对厌氧氨氧化的影响不容忽视。在这项工作中，从宏观到微观层面剖析了厌氧氨氧化对 MC-LR 的反应机制。光谱学和流变学工具表明，胞外聚合物物质 （EPS） 提供的氢键力和污泥相对稳定的屈服应力赋予了厌氧氨氧化颗粒抵抗变形的能力，以维持氮代谢。厌氧氨氧化过程可以在生物学水平上适应性地对抗 MC-LR。在 1 mg/L MC-LR 时，功能微生物 （Candidatus Brocadia 和 Candidatus Kuenenia） 和核心基因 （hzs 和 hdh） 的相对丰度增加以进行自我维持，而在 3 mg/L MC-LR 时，反硝化菌的丰度增加 7.72%，以防止氮代谢进一步崩溃。值得注意的是，高浓度的具有抗降解性能的 MC-LR 会穿透 EPS 屏障，扰乱细胞内的抗氧化平衡并攻击呼吸链，从而直接破坏氮转化和电子转移，导致脱氮效率降低 25.6%。计算化学进一步证明 MC-LR 偶联细胞内生物分子以影响生物学功能。这项工作提供了对 MC-LR 在厌氧氨氧化中的命运和风险的见解。

环境影响

MC-LR 的高持久性、抗氧化性和生物毒性严重威胁着人类健康和水生系统。在这项工作中，全面剖析了厌氧氨氧化对 MC-LR 的反应机制。氢键力、增加的污泥产量应力和厌氧氨氧化转化为反硝化作用的适应性调节机制赋予厌氧氨氧化菌抵抗变形的能力。然而，MC-LR 具有抗降解性，它扰乱了细胞内的抗氧化平衡，攻击了呼吸链并结合了细胞内生物分子，从而影响了厌氧氨氧化功能。这项研究揭示了 MC-LR 在厌氧氨氧化中的命运，并激发了人们对其他生物废水处理过程如何响应 MC-LR 干扰的日益关注。