磺胺类抗生素(SAs)是生态系统和环境的严重污染物。以前的研究表明,SAs如磺胺甲恶唑(SMX)的微生物降解是通过sad编码的氧化途径进行的,而磺酰胺抗性二氢蝶呤合酶基因,sul,负责SA抗性。然而,悲伤和sul基因的共同出现,以及sul基因如何影响SMX降解,没有被探索。在这项研究中,两种SMX降解细菌菌株,SD-1和SD-2是从SMX降解富集中培养的。两种菌株都是Paenjoartbacter物种,并且在系统发育上相同;但是,它们表现出不同的SMX降解活性。具体来说,菌株SD-1利用SMX作为生长的唯一碳源和能源,是一种高效的SMX降解剂,而SD-2不能使用SMX作为唯一的碳源或能源,并且在提供额外的碳源时显示出有限的SMX降解。基因组注释,增长,酶活性测试,和代谢物检测表明,菌株SD-1和SD-2共享一个sad编码的SMX降解氧化途径和原儿茶酸降解途径。一个新的耐磺胺二氢蝶呤合成酶基因,sul918,在菌株SD-1中鉴定,但在SD-2中未鉴定。此外,sul918的缺乏导致菌株SD-2的SMX降解活性较低。基因组数据挖掘揭示了sad和sul基因在有效的SMX降解性节肢动物菌株中的共同出现。我们建议磺酰胺抗性二氢蝶呤合酶和sad基因的共存对于有效的SMX生物降解至关重要。两个具有不同降解活性的磺胺甲恶唑降解菌株,Paenacartactersp.SD-1和Paenjoartbactersp.分离并鉴定SD-2。•菌株SD-1和SD-2共享用于SMX降解的悲伤编码的氧化途径。•菌株SD-1的新质粒携带的SMX抗性基因(sul918)在SMX降解效率中起着至关重要的作用。
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.