Evaluation of Sulfadiazine Degradation in Three Newly Isolated Pure Bacterial Cultures

This study is aimed to assess the biodegradation of sulfadiazine (SDZ) and characterization of heavy metal resistance in three pure bacterial cultures and also their chemotactic response towards 2-aminopyrimidine. The bacterial cultures were isolated from pig manure, activated sludge and sediment samples, by enrichment technique on SDZ (6 mg L-1). Based on the 16S rRNA gene sequence analysis, the microorganisms were identified within the genera of Paracoccus, Methylobacterium and Kribbella, which were further designated as SDZ-PM2-BSH30, SDZ-W2-SJ40 and SDZ-3S-SCL47. The three identified pure bacterial strains degraded up to 50.0, 55.2 and 60.0% of SDZ (5 mg L-1), respectively within 290 h. On the basis of quadrupole time-of-flight mass spectrometry and high performance liquid chromatography, 2-aminopyrimidine and 4-hydroxy-2-aminopyrimidine were identified as the main intermediates of SDZ biodegradation. These bacteria were also able to degrade the metabolite, 2-aminopyrimidine, of the SDZ. Furthermore, SDZ-PM2-BSH30, SDZ-W2-SJ40 and SDZ-3S-SCL47 also showed resistance to various heavy metals like copper, cadmium, chromium, cobalt, lead, nickel and zinc. Additionally, all three bacteria exhibited positive chemotaxis towards 2-aminopyrimidine based on the drop plate method and capillary assay. The results of this study advanced our understanding about the microbial degradation of SDZ, which would be useful towards the future SDZ removal in the environment.

本研究旨在评估磺胺嘧啶（sulfadiazine, SDZ）的生物降解效果，表征3株纯培养细菌的重金属抗性，并探究其对2-氨基嘧啶的趋化响应。实验采用富集培养法，以6 mg·L⁻¹的磺胺嘧啶为选择底物，从猪粪、活性污泥与沉积物样本中分离得到目标细菌菌株。通过16S rRNA基因序列分析，将这3株微生物分别鉴定归属于副球菌属（Paracoccus）、甲基杆菌属（Methylobacterium）和克里贝拉菌属（Kribbella），并命名为SDZ-PM2-BSH30、SDZ-W2-SJ40与SDZ-3S-SCL47。在290小时的培养周期内，这3株纯培养菌株对初始浓度为5 mg·L⁻¹的磺胺嘧啶的降解率分别可达50.0%、55.2%与60.0%。借助四极杆飞行时间质谱（quadrupole time-of-flight mass spectrometry）与高效液相色谱（high performance liquid chromatography）分析，鉴定出2-氨基嘧啶与4-羟基-2-氨基嘧啶为磺胺嘧啶生物降解的主要中间产物。同时，这3株细菌均可降解磺胺嘧啶的代谢中间产物2-氨基嘧啶。进一步实验表明，SDZ-PM2-BSH30、SDZ-W2-SJ40与SDZ-3S-SCL47对铜、镉、铬、钴、铅、镍及锌等多种重金属均具有抗性。此外，通过点滴平板法与毛细管分析法验证，3株细菌均对2-氨基嘧啶呈现正向趋化性。本研究结果深化了对磺胺嘧啶微生物降解机制的认知，可为未来环境中磺胺嘧啶的去除修复提供理论参考。