Although partial denitrification coupled with the anammox process has received considerable attention, the partial denitrification function of companion bacteria in mixotrophic anammox systems remains experimentally investigated. Herein, a partial denitrification process was realized in mixotrophic anammox systems with a COD/TN ratio of 0.75. Furthermore, the experimental verification results revealed that nitrate and ammonia were eliminated concurrently, showing that partial denitrifying bacteria were present in the mixotrophic anammox systems. Denitratisoma and Norank Xanthobacteraceae were the dominant genera of companion bacteria containing functional genes related to partial denitrification. Especially, Denitratisoma was a companion bifunctional bacterium for Candidatus Kuenenia shifted between complete and partial denitrification at different COD/TN ratios. Moreover, nir gene abundance in the mixotrophic anammox system increased by 135.4 % compared to that in the autotrophic anammox system. In contrast, nor gene abundance decreased by 28.00 %, indicating that NO might be used as a medium for cross-feeding anammox and partial denitrification. This study provides a more thorough understanding of companion bacteria in mixotrophic anammox systems.

中文翻译：

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破译不同碳/氮比下混合营养型厌氧氨氧化系统中伴生菌的部分反硝化功能


尽管部分反硝化与厌氧氨氧化过程相结合受到了相当大的关注，但混合营养厌氧氨氧化系统中伴生菌的部分反硝化功能仍在实验研究中。在此，在 COD/TN 比值为 0.75 的混合营养厌氧氨氧化系统中实现了部分反硝化过程。此外，实验验证结果表明，硝酸盐和氨同时被消除，表明混合营养型厌氧氨氧化系统中存在部分反硝化细菌。Denitratisoma 和 Norank Xanthobacteraceae 是包含与部分反硝化相关的功能基因的伴生菌的优势属。特别是，Denitratisoma 是 Candidatus Kuenenia 的伴生双功能细菌，以不同的 COD/TN 比率在完全和部分反化之间转换。此外，与自养厌氧氨氧化系统相比，混合营养型厌氧氨氧化系统中的 nir 基因丰度增加了 135.4%。相比之下，NOR 基因丰度下降了 28.00 %，表明 NO 可能用作交叉喂养厌氧氨氧化和部分反氮化的培养基。这项研究提供了对混合营养型厌氧氨氧化系统中的伴侣细菌的更透彻的了解。