Beijing International Scientific and Technological Cooperation Base of Water Pollution Control Techniques for Antibiotics and Resistance Genes, Beijing Key Laboratory of Aqueous Typical Pollutants Control and Water Quality Safeguard, School of Environment, Beijing Jiaotong University, Beijing 100044, PR China.
Key Laboratory of Energy-Water Conservation and Wastewater Resources Recovery of China National Light Industry, Institute of Resources and Environment, Beijing Academy of Science and Technology, Beijing 100095, PR China.
Sci Total Environ. 2023 Apr 15;869:161897. doi: 10.1016/j.scitotenv.2023.161897. Epub 2023 Jan 26.
Anaerobic ammonium oxidation (anammox) has been widely used for the sustainable removal of nitrogen from wastewater. Extracellular DNA (exDNA), as one of the main components of biofilms, not only determines the initial formation process, but also allows the three-dimensional structure to be maintained. Since the effects of exDNA on anammox biofilm formation are still poorly understood, this study elucidated the effects of exDNA on different stages of anammox biofilm establishment and maintenance under static conditions and its mechanism. The results revealed that exDNA mainly affected the maintenance stage of anammox biofilm formation. Compared with the absence of exDNA, nitrogen removal efficiency in the presence of exDNA was 6.17 % higher; the number of bacteria cells attached to the carrier was 2.23 times that in the absence of exDNA. The spatiotemporal distribution of bacteria was revealed by fluorescence in situ hybridization. After 30 days, the relative abundances of anammox in biofilms were 6.19 % and 0.4 % in the presence and absence of exDNA, respectively, indicating its positive role in anammox bacteria (AnAOB) adhesion and biofilm formation. The presence of exDNA in extracellular polymeric substances (EPS) promotes the synthesis of proteins and soluble microbial products. According to the extended Derjaguin-Landau-Verwey-Overbeek (X - DLVO) theory, the presence of exDNA also reduced the Lewis acid-base interaction energy and created favorable thermodynamic conditions for AnAOB adhesion. These findings advance our understanding of the role of exDNA in anammox-mediated biofilm formation and offer insights into the mechanism of exDNA in the establishment and maintenance stages.
厌氧氨氧化（anammox）已被广泛应用于可持续去除废水中的氮。胞外 DNA（exDNA）作为生物膜的主要成分之一，不仅决定了初始形成过程，还维持了三维结构。由于 exDNA 对厌氧氨氧化生物膜形成的影响仍知之甚少，本研究阐明了 exDNA 在静态条件下对厌氧氨氧化生物膜形成和维持的不同阶段的影响及其机制。结果表明，exDNA 主要影响厌氧氨氧化生物膜形成的维持阶段。与不存在 exDNA 相比，存在 exDNA 时的氮去除效率提高了 6.17%；附着在载体上的细菌细胞数量是不存在 exDNA 时的 2.23 倍。通过荧光原位杂交揭示了细菌的时空分布。30 天后，生物膜中厌氧氨氧化菌（AnAOB）的相对丰度分别为存在和不存在 exDNA 时的 6.19%和 0.4%，表明其在厌氧氨氧化菌（AnAOB）附着和生物膜形成中发挥了积极作用。胞外聚合物物质（EPS）中存在 exDNA 会促进蛋白质和可溶性微生物产物的合成。根据扩展的德热加伦-兰德维厄-奥弗贝克（X-DLVO）理论，exDNA 的存在还降低了路易斯酸碱相互作用能，并为 AnAOB 附着创造了有利的热力学条件。这些发现提高了我们对 exDNA 在厌氧氨氧化介导的生物膜形成中的作用的认识，并深入了解了 exDNA 在建立和维持阶段的作用机制。
