To alleviate the negative effects of perfluorooctanoic acid (PFOA) on nitrogen removal via anaerobic ammonia oxidation (anammox), an exogenous signaling factor (N-hexanoyl-L-homoserine lactone, C6-HSL) was introduced into an anammox reactor. Results showed that 2 μmol/L C6-HSL promoted the nitrogen removal efficiency of the anammox reactor under PFOA stress, with the removal efficiencies of ammonia and nitrite increasing from 79.7 ± 4.8 % and 80.8 ± 3.8 %, to 94.4 ± 4.3 % and 97.1 ± 3.8 %. Exogenous C6-HSL enhanced the compactness of the extracellular proteins, and improved the sludge hydrophobicity. Meanwhile, C6-HSL resulted in a microbial shift, with the relative abundance of Planctomycetes increasing from 30.2 % to 49.5 %. Candidatus Kuenenia stuttgartiensis replaced Candidatus Brocadia sp. BL1 as the dominant species, while the available space for other nitrogen-removing bacteria was reduced. Exogenous C6-HSL promoted the expression of anammox-related genes, such as hzsB and hdh, while denitrifying genes were down-regulated. In addition, the relative abundance of HdtS, which synthesizes AHLs, increased by 0.02446%.

中文翻译：

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宏基因组和细胞外聚合物分析揭示了外源性 N-己酰-L-高丝氨酸内酯减轻全氟辛酸对厌氧氨氧化过程的抑制作用的机制。

为了减轻全氟辛酸 (PFOA) 对厌氧氨氧化 (anammox) 脱氮的负面影响，将外源信号因子（N-己酰-L-高丝氨酸内酯，C6-HSL）引入厌氧氨氧化反应器。结果表明，2 μmol/L C6-HSL 促进了厌氧氨氧化反应器在 PFOA 胁迫下的脱氮效率，氨和亚硝酸盐的去除效率分别从 79.7 ± 4.8 % 和 80.8 ± 3.8 % 提高到 94.4 ± 4.3 % 和 97.1 ± 3.8 %。外源性C6-HSL增强了细胞外蛋白的致密性，改善了污泥的疏水性。同时，C6-HSL 导致微生物转变，Planctomycetes 的相对丰度从 30.2% 增加到 49.5%。Candidatus Kuenenia stuttgartiensis 取代了 Candidatus Brocadia sp。BL1为优势种，而其他除氮细菌的可用空间减少了。外源性 C6-HSL 促进厌氧氨氧化相关基因的表达，如 hzsB 和 hdh，而反硝化基因被下调。此外，合成AHL的HdtS的相对丰度增加了0.02446%。