CAS Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China; State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; Hubei Key Laboratory of Wetland Evolution & Ecological Restoration, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China.
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Sci Total Environ. 2021 Sep 1;785:147282. doi: 10.1016/j.scitotenv.2021.147282. Epub 2021 Apr 23.
Pond-ditch circulation system (PDCS) is a promising remediation strategy for rural wastewater treatment. Aquatic plants play nonnegligible roles in the nutrient removal of the PDCS. However, mechanisms of root exudates regulating nutrient removal in PDCSs remained unclear. In our study, the PDCS achieved higher total nitrogen (TN) and phosphorus (TP) removal rates (72.7-97.4%) compared to the static system. Protein contents in root exudates of the PDCS ranged from 0.041 to 1.332 mg L, showing negative associations with Simpson index. Lactic acid and tartaric acid in the PDCS varied from 0.045 to 0.380 mg L and 0.024 to 5.446 mg L, which were tightly linked with TN, TP, and TP removal rates and most sediment properties, especially sediment total nitrogen (STN) and total organic carbon (TOC), and sediment inorganic phosphorus (SIP). Moreover, the top 3 relative dominant genus were Bacillus (0.11%-17.90%), Geobacter (0.35%-12.04%), and Clostridium sensu stricto 1 (0.14%-12.05%), which might be the predominant groups in nutrient removal of PDCSs. RDA results indicated that lactic acid, protein, and amino acids were positively correlated with Geobacter; while Bacillus was significantly affected by water content. Path analysis further demonstrated that the indirect effect of secretion from plant roots on nutrient removal rates was mainly through modulating bacteria diversity and relative abundance. Taken together, root exudates, especially protein, amino acids, and lactic acid, altered rhizosphere microbial relative abundance and diversity, where the impacts were bacterial species-dependent.
池塘沟渠循环系统（PDCS）是一种很有前途的农村废水处理策略。水生植物在 PDCS 的养分去除中起着不可忽视的作用。然而，根系分泌物调节 PDCS 中养分去除的机制尚不清楚。在我们的研究中，PDCS 实现了比静态系统更高的总氮（TN）和总磷（TP）去除率（72.7-97.4%）。PDCS 根系分泌物中的蛋白质含量在 0.041 到 1.332 毫克/升之间，与 Simpson 指数呈负相关。PDCS 中的乳酸和酒石酸含量在 0.045 到 0.380 毫克/升和 0.024 到 5.446 毫克/升之间，与 TN、TP 和 TP 去除率以及大多数沉积物特性，特别是沉积物总氮（STN）和总有机碳（TOC）以及沉积物无机磷（SIP）紧密相关。此外，前 3 个相对优势属为芽孢杆菌（0.11%-17.90%）、地杆菌（0.35%-12.04%）和严格梭菌 1（0.14%-12.05%），它们可能是 PDCS 中养分去除的主要类群。RDA 结果表明，乳酸、蛋白质和氨基酸与地杆菌呈正相关；而芽孢杆菌受含水量的显著影响。路径分析进一步表明，植物根系分泌物对养分去除率的间接影响主要是通过调节细菌多样性和相对丰度来实现的。总之，根系分泌物，特别是蛋白质、氨基酸和乳酸，改变了根际微生物的相对丰度和多样性，这种影响取决于细菌种类。
