A novel sulfonamide resistance mechanism by two-component flavin-dependent monooxygenase system in sulfonamide-degrading actinobacteria
A novel sulfonamide resistance mechanism by two-component flavin-dependent monooxygenase system in sulfonamide-degrading actinobacteria
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DOI：
10.1016/j.envint.2019.03.046
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发表时间：
2019-06-01
影响因子：
11.8
通讯作者：
Cha, Chang-Jun
中科院分区：
文献类型：
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作者：
Kim, Dae-Wi;Thawng, Cung Nawl;Cha, Chang-Jun
磺胺降解菌已在各种环境中被发现，这表明通过药物灭活存在新的耐药机制。在这项研究中，能够利用各种磺胺作为唯一碳源的微杆菌属CJ 77从堆肥设施中分离。基因组和蛋白质组分析表明，一个基因簇含有一个黄素依赖性单加氧酶和黄素还原酶高度上调响应磺胺类药物。生化分析表明，双组分单加氧酶系统是磺胺类药物初始裂解的关键酶。大肠杆菌中的双组分系统的共表达赋予磺胺甲恶唑的敏感性降低，表明编码药物失活酶的基因是潜在的耐药决定因素。比较基因组分析表明，基因簇含有磺胺单加氧酶（更名为sulX）和黄素还原酶（sulR）是高度保守的基因组岛之间共享的磺胺降解放线菌，所有这些也含有sul1携带1类整合子。这些结果表明，磺胺代谢可能已经演变的磺胺耐药菌已经获得了磺胺选择压力下的1类整合子。此外，存在多个插入序列元件和假定的复合转座子结构含有sulX基因簇表示潜在的动员。这是第一项研究报告，sulX负责磺胺降解和耐药性普遍存在于磺胺降解放线菌和其遗传特征表明水平基因转移的新的耐药基因。
Sulfonamide-degrading bacteria have been discovered in various environments, suggesting the presence of novel resistance mechanisms via drug inactivation. In this study, Microbacterium sp. CJ77 capable of utilizing various sulfonamides as a sole carbon source was isolated from a composting facility. Genome and proteome analyses revealed that a gene cluster containing a flavin-dependent monooxygenase and a flavin reductase was highly up-regulated in response to sulfonamides. Biochemical analysis showed that the two-component monooxygenase system was key enzymes for the initial cleavage of sulfonamides. Co-expression of the two-component system in Escherichia coli conferred decreased susceptibility to sulfamethoxazole, indicating that the genes encoding drug-inactivating enzymes are potential resistance determinants. Comparative genomic analysis revealed that the gene cluster containing sulfonamide monooxygenase (renamed as sulX) and flavin reductase (sulR) was highly conserved in a genomic island shared among sulfonamide-degrading actinobacteria, all of which also contained sul1-carrying class 1 integrons. These results suggest that the sulfonamide metabolism may have evolved in sulfonamide-resistant bacteria which had already acquired the class 1 integron under sulfonamide selection pressures. Furthermore, the presence of multiple insertion sequence elements and putative composite transposon structures containing the sulX gene cluster indicated potential mobilization. This is the first study to report that sulX responsible for both sulfonamide degradation and resistance is prevalent in sulfonamide-degrading actinobacteria and its genetic signatures indicate horizontal gene transfer of the novel resistance gene.