Microbial community may respond to different adverse conditions and result in the variation of extracellular polymeric substances (EPS) in denitrification biofilm; this study discovered the role of EPS in accordance with the analysis of cyclic diguanylate (c‐di‐GMP) and electron equilibrium (EE) under low organic loading rate, shock organic loading rate and low temperature conditions. Good nitrate removal performance could be achieved under shock organic loading rate and low temperature conditions; however, owing to the low organic loading rate, the carbon source was preferentially utilized for biomass growth. Tightly bound EPS (TB‐EPS) contents progressively increased and facilitated cell adhesion and biofilm formation. The stable TB protein (TB‐PN) content in TB‐EPS built a cross‐linked network to maintain internal biofilm structure and led to the rapid biosynthesis of polysaccharides, which could further enhance microbial adhesion and improve nitrate removal. C‐di‐GMP played an important role in biomass retention and biofilm formation, based on the correlation analysis of c‐di‐GMP and EPS. TB polysaccharide (TB‐PS) contents presented a significant positive correlation with c‐di‐GMP content, microbial adhesion and biofilm stabilization was further enhanced through c‐di‐GMP regulation. In addition, a remarkable negative correlation between electron deletion rate (EDR) and TB‐PN and TB‐PS was discovered, and TB‐PS was required to serve as energy source to enhance denitrification according to EE analysis. Surprisingly, dynamic microbial community was observed due to the drastic community succession under low temperature conditions, and the discrepancy between the dominant species for denitrification was found under shock organic loading rate and low temperature conditions. The notable increase in bacterial strains Simlicispira, Pseudomonas and Chryseobacterium was conducive to biofilm formation and denitrification under shock organic loading rate, while Dechloromonas and Zoogloea dramatically enriched for nitrate removal under low temperature conditions. The high abundance of Dechloromonas improved the secretion of EPS through the downstream signal transduction, and the c‐di‐GMP conserved in Pseudomonas concurrently facilitated to enhance exopolysaccharide production to shock organic loading rate and low temperature conditions.

中文翻译：

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暴露于不利条件下的反硝化生物膜中细胞外聚合物与微生物群落结构的相关性。

微生物群落可能对不同的不利条件作出反应，并导致反硝化生物膜中细胞外聚合物的变化。这项研究根据低有机负荷率，有机冲击负荷率和低温条件下环状双鸟苷酸（c-di-GMP）和电子平衡（EE）的分析发现了EPS的作用。在冲击有机负荷率和低温条件下，可以获得良好的硝酸盐去除性能；然而，由于有机负荷率低，碳源优先用于生物质的生长。紧密结合的EPS（TB-EPS）含量逐渐增加，并促进细胞粘附和生物膜形成。TB-EPS中稳定的TB蛋白（TB-PN）含量建立了一个交联网络，以维持内部生物膜结构，并导致多糖的快速生物合成，这可以进一步增强微生物的附着力并改善硝酸盐的去除。基于c-di-GMP和EPS的相关性分析，C-di-GMP在生物量保留和生物膜形成中发挥了重要作用。TB多糖（TB-PS）含量与c-di-GMP含量呈显着正相关，通过c-di-GMP调节可进一步增强微生物粘附和生物膜稳定性。此外，发现电子缺失率（EDR）与TB-PN和TB-PS之间存在显着的负相关，根据EE分析，要求TB-PS作为能量来增强反硝化作用。出奇，在低温条件下，由于微生物群落的剧烈演替而观察到了动态微生物群落，而在激增有机物负荷率和低温条件下，反硝化的优势种之间存在差异。细菌菌株显着增加Simlicispira，Pseudomonas和Chryseobacterium有助于在冲击有机负荷速率下形成生物膜和反硝化作用，而Dechloromonas和Zoogloea在低温条件下显着富集硝酸盐去除作用。丰富的十氯单胞菌通过下游信号转导改善了EPS的分泌，假单胞菌中保守的c-di-GMP同时促进了胞外多糖的产生，从而提高了有机负荷率和低温条件。