School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou, 310012, China.
J Environ Manage. 2024 Apr;356:120750. doi: 10.1016/j.jenvman.2024.120750. Epub 2024 Mar 22.
The nitrate denitrifying anaerobic methane oxidation-anaerobic ammonia oxidation (DAMO-anammox) can accomplish nitrogen removal and methane (CH) reduction. This process greatly contributes to carbon emission mitigation and carbon neutrality. In this study, we investigated the electron transfer process of functional microorganisms in the iron-mediated DAMO-anammox system. Fe could be bound to several functional groups (-CH, COO-, -CH) in extracellular polymeric substance (EPS), and the functional groups bound were different at different iron concentration. Fe underwent reduction reactions to produce Fe. Most Fe and Fe react with microorganisms and formed chelates with EPS. Three-dimensional fluorescence spectra showed that Fe affected the secretion of tyrosine and tryptophan, which were essential for cytochrome synthesis. The presence of Fe accelerated c-type cytochrome-mediated extracellular electron transfer (EET), and when more Fe existed, the more cytochrome C expressed. DAMO archaea (M. nitroreducens) in the system exhibited a high positive correlation with the functional genes (resa and ccda) for cytochrome c synthesis. Some denitrifying microorganisms showed positive correlations with the abundance of riboflavin. This finding showed that riboflavin secreted by functional microorganisms acted as an electron shuttle. In addition, DAMO archaea were positively correlated with the hair synthesis gene pily1, which indicated that direct interspecies electron transfer (DIET) may exist in the iron-mediated DAMO-anammox system.
硝酸盐异化型厌氧甲烷氧化-厌氧氨氧化（DAMO-anammox）可以实现氮的去除和甲烷（CH）的还原。这一过程对减少碳排放和实现碳中和贡献巨大。本研究探讨了铁介导的 DAMO-anammox 系统中功能微生物的电子传递过程。铁可与胞外聚合物（EPS）中的几种功能基团（-CH、COO-、-CH）结合，而不同铁浓度下结合的功能基团也不同。铁经历还原反应生成 Fe。大多数 Fe 和 Fe 与微生物反应，并与 EPS 形成螯合物。三维荧光光谱表明，Fe 影响酪氨酸和色氨酸的分泌，这是细胞色素合成所必需的。Fe 的存在加速了 c 型细胞色素介导的细胞外电子传递（EET），当存在更多的 Fe 时，细胞色素 C 的表达就越多。系统中的厌氧氨氧化古菌（M. nitroreducens）与细胞色素 c 合成的功能基因（resa 和 ccda）呈高度正相关。一些反硝化微生物与核黄素的丰度呈正相关。这一发现表明，功能微生物分泌的核黄素充当了电子穿梭体。此外，厌氧氨氧化古菌与毛发生成基因 pily1 呈正相关，这表明在铁介导的 DAMO-anammox 系统中可能存在直接种间电子传递（DIET）。
