State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, 712100, Shaanxi, China.
State Key Laboratory of Microbial Resources and Environmental Microbiology Research Center at Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.
Appl Microbiol Biotechnol. 2023 Sep;107(18):5813-5827. doi: 10.1007/s00253-023-12679-x. Epub 2023 Jul 13.
Sulfonamide antibiotics (SAs) are serious pollutants to ecosystems and environments. Previous studies showed that microbial degradation of SAs such as sulfamethoxazole (SMX) proceeds via a sad-encoded oxidative pathway, while the sulfonamide-resistant dihydropteroate synthase gene, sul, is responsible for SA resistance. However, the co-occurrence of sad and sul genes, as well as how the sul gene affects SMX degradation, was not explored. In this study, two SMX-degrading bacterial strains, SD-1 and SD-2, were cultivated from an SMX-degrading enrichment. Both strains were Paenarthrobacter species and were phylogenetically identical; however, they showed different SMX degradation activities. Specifically, strain SD-1 utilized SMX as the sole carbon and energy source for growth and was a highly efficient SMX degrader, while SD-2 did could not use SMX as a sole carbon or energy source and showed limited SMX degradation when an additional carbon source was supplied. Genome annotation, growth, enzymatic activity tests, and metabolite detection revealed that strains SD-1 and SD-2 shared a sad-encoded oxidative pathway for SMX degradation and a pathway of protocatechuate degradation. A new sulfonamide-resistant dihydropteroate synthase gene, sul918, was identified in strain SD-1, but not in SD-2. Moreover, the lack of sul918 resulted in low SMX degradation activity in strain SD-2. Genome data mining revealed the co-occurrence of sad and sul genes in efficient SMX-degrading Paenarthrobacter strains. We propose that the co-occurrence of sulfonamide-resistant dihydropteroate synthase and sad genes is crucial for efficient SMX biodegradation. KEY POINTS: • Two sulfamethoxazole-degrading strains with distinct degrading activity, Paenarthrobacter sp. SD-1 and Paenarthrobacter sp. SD-2, were isolated and identified. • Strains SD-1 and SD-2 shared a sad-encoded oxidative pathway for SMX degradation. • A new plasmid-borne SMX resistance gene (sul918) of strain SD-1 plays a crucial role in SMX degradation efficiency.
磺胺类抗生素（SAs）是对生态系统和环境的严重污染物。先前的研究表明，微生物通过 sad 编码的氧化途径降解磺胺类药物，如磺胺甲恶唑（SMX），而磺胺类药物抗性二氢蝶酸合酶基因 sul 则负责磺胺类药物抗性。然而，sad 和 sul 基因的共存以及 sul 基因如何影响 SMX 降解尚未得到探索。在这项研究中，从 SMX 降解富集物中培养了两株 SMX 降解细菌菌株 SD-1 和 SD-2。这两种菌株均为节杆菌属，在系统发育上相同；然而，它们表现出不同的 SMX 降解活性。具体而言，菌株 SD-1 将 SMX 用作生长的唯一碳源和能源，是一种高效的 SMX 降解剂，而 SD-2 不能将 SMX 用作唯一碳源或能源，并且在提供额外碳源时表现出有限的 SMX 降解。基因组注释、生长、酶活性测试和代谢物检测表明，菌株 SD-1 和 SD-2 共享 sad 编码的 SMX 氧化途径和原儿茶酸降解途径。在菌株 SD-1 中鉴定出一种新的磺胺类抗性二氢蝶酸合酶基因 sul918，但在 SD-2 中未鉴定出。此外，sul918 的缺乏导致 SD-2 中 SMX 降解活性低。基因组数据挖掘揭示了高效 SMX 降解节杆菌属菌株中 sad 和 sul 基因的共存。我们提出，磺胺类药物抗性二氢蝶酸合酶和 sad 基因的共存对于高效的 SMX 生物降解至关重要。 关键点： • 分离并鉴定了两种具有不同降解活性的磺胺甲恶唑降解菌株，节杆菌属 SD-1 和节杆菌属 SD-2。 • 菌株 SD-1 和 SD-2 共享 sad 编码的 SMX 氧化途径。 • 菌株 SD-1 中新的质粒携带的 SMX 抗性基因（sul918）在 SMX 降解效率中起着关键作用。
