Guangdong Provincial Engineering Research Center for Urban Water Recycling and Environmental Safety, Graduate School at Shenzhen, Tsinghua University, Shenzhen, China; School of Environment, Tsinghua University, Beijing, China.
Guangdong Provincial Engineering Research Center for Urban Water Recycling and Environmental Safety, Graduate School at Shenzhen, Tsinghua University, Shenzhen, China; School of Environment, Tsinghua University, Beijing, China; Shenzhen Engineering Research Laboratory for Sludge and Food Waste Treatment and Resource Recovery, Graduate School at Shenzhen, Tsinghua University, China.
Environ Int. 2019 Oct;131:104961. doi: 10.1016/j.envint.2019.104961. Epub 2019 Jul 19.
Biodegradation is an important route for the removal of sulfamethazine (SMZ), one of the most commonly used sulfonamide antibiotics, in the environment. However, little information is known about the kinetics, products, and pathways of SMZ biodegradation owing to the complexity of its enzyme-based biotransformation processes. In this study, the SMZ-degrading strain A01 belonging to the genus Paenarthrobacter was isolated from SMZ-enriched activated sludge reactors. The bacterial cells were rod-shaped with transient branches 2.50-4.00 μm in length with most forming in a V-shaped arrangement. The genome size of Paenarthrobacter sp. A01 had a total length of 4,885,005 bp with a GC content of 63.5%, and it contained 104 contigs and 55 RNAs. The effects of pH, temperature, initial substrate concentration and additional carbon source on the biodegradation of SMZ were investigated. The results indicated that pH 6.0-7.8, 25 °C and the addition of 0.2 g/L sodium acetate favored the biodegradation, whereas a high concentration of SMZ, 500 mg/L, had an inhibitory effect. The biodegradation kinetics with SMZ as the sole carbon source or 0.2 g/L sodium acetate as the co-substrate fit the modified Gompertz model well with a correlation coefficient (R) of 0.99. Three biodegradation pathways were proposed involving nine biodegradation products, among which CHNOS and CHN were two novel biodegradation products that have not been reported previously. Approximately 90.7% of SMZ was transformed to 2-amino-4, 6-dimethylpyrimidine. Furthermore, sad genes responsible for catabolizing sulfonamides were characterized in A01 with high similarities of 96.0%-100.0%. This study will fill the knowledge gap in the biodegradation of this ubiquitous micropollutant in the aquatic environment.
磺胺甲恶唑（SMZ）是环境中最常用的磺胺类抗生素之一，其生物降解是其去除的重要途径。然而，由于其基于酶的生物转化过程复杂，对于 SMZ 生物降解的动力学、产物和途径知之甚少。在这项研究中，从磺胺甲恶唑富集的活性污泥反应器中分离到属于节杆菌属的 SMZ 降解菌株 A01。细菌细胞呈杆状，长度为 2.50-4.00 μm，有短暂的分支，大多数呈 V 形排列。节杆菌属 A01 的基因组大小为 4885005 bp，GC 含量为 63.5%，包含 104 个 contigs 和 55 个 RNA。研究了 pH、温度、初始底物浓度和外加碳源对 SMZ 生物降解的影响。结果表明，pH 值为 6.0-7.8、25°C 和添加 0.2 g/L 乙酸钠有利于生物降解，而高浓度的 SMZ（500mg/L）则具有抑制作用。以 SMZ 为唯一碳源或以 0.2 g/L 乙酸钠为共底物的生物降解动力学均符合修正的 Gompertz 模型，相关系数（R）为 0.99。提出了三条生物降解途径，涉及九个生物降解产物，其中 CHNOS 和 CHN 是两种以前未报道过的新型生物降解产物。约 90.7%的 SMZ 转化为 2-氨基-4,6-二甲基嘧啶。此外，A01 中还鉴定出了负责降解磺胺类抗生素的 sad 基因，其相似度高达 96.0%-100.0%。本研究将填补该普遍存在的水环境污染微污染物生物降解知识空白。
