Li Mengting, Chen Zhipeng, Li Xiang, Yu Sheng, Xu Shiling, Qiu Shuang, Ge Shijian
Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Xiao Ling Wei 200, Nanjing 210094, Jiangsu, China.
Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Xiao Ling Wei 200, Nanjing 210094, Jiangsu, China.
Water Res. 2025 Jul 15;280:123473. doi: 10.1016/j.watres.2025.123473. Epub 2025 Mar 9.
The integration of microalgal-bacterial consortium (MBC) with partial nitrification (PN-MBC) offers a promising strategy for low-carbon wastewater treatment. However, the gradually accumulated nitrite levels challenge microalgal activities and system stability. This study demonstrated the nitrite tolerance (10-300 mg/L) of Chlorella sp., isolated from the PN-MBC system, and the underlying mechanism. Physiological assays, transcriptomic analysis, and bioinformatics revealed that nitrite significantly affected photosynthesis, DNA processing, carbon metabolism, signal transduction, and protein processing. Specifically, nitrite inhibited photosystem II by targeting the PsbO subunit, disrupting electron transport and the proton gradient, hindering carbon fixation in the Calvin cycle. It also caused DNA damage, including strand breaks, base modifications and mismatches, with upregulated DNA repair pathways and biomass growth stagnation between Days 5-7. In response, Chlorella sp. upregulated carbon metabolism and oxidative phosphorylation to enhance ATP synthesis, while exopolysaccharides were secreted for energy storage, and protein processing was downregulated to mitigate proteotoxic stress. Evolution analysis suggested that active site variations in carbon metabolism enzymes contributed to Chlorella sp.'s enhanced nitrite resilience. These findings advance current understandings of nitrite's effects on microalgae and offer insights for optimizing PN-MBC performance under high-nitrite conditions.
微藻-细菌联合体（MBC）与部分硝化作用（PN-MBC）相结合为低碳污水处理提供了一种有前景的策略。然而，亚硝酸盐水平的逐渐积累对微藻活性和系统稳定性构成挑战。本研究证明了从PN-MBC系统中分离出的小球藻对亚硝酸盐的耐受性（10-300毫克/升）及其潜在机制。生理分析、转录组分析和生物信息学表明，亚硝酸盐显著影响光合作用、DNA处理、碳代谢、信号转导和蛋白质加工。具体而言，亚硝酸盐通过靶向PsbO亚基抑制光系统II，破坏电子传递和质子梯度，阻碍卡尔文循环中的碳固定。它还导致DNA损伤，包括链断裂、碱基修饰和错配，DNA修复途径上调，生物量在第5至7天生长停滞。作为响应，小球藻上调碳代谢和氧化磷酸化以增强ATP合成，同时分泌胞外多糖用于能量储存，并下调蛋白质加工以减轻蛋白毒性应激。进化分析表明，碳代谢酶的活性位点变异有助于小球藻增强对亚硝酸盐的恢复力。这些发现推进了目前对亚硝酸盐对微藻影响的认识，并为在高亚硝酸盐条件下优化PN-MBC性能提供了见解。
