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首页> 外文期刊>Journal of bacteriology >Expression of Multidrug Resistance Efflux Pump Gene norA Is Iron Responsive in Staphylococcus aureus
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Expression of Multidrug Resistance Efflux Pump Gene norA Is Iron Responsive in Staphylococcus aureus

机译：多药耐药外排泵基因norA在金黄色葡萄球菌中对铁有响应

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Staphylococcus aureus utilizes efflux transporter NorA to pump out a wide range of structurally dissimilar drugs, conferring low-level multidrug resistance. The regulation of norA expression has yet to be fully understood although past studies have revealed that this gene is under the control of the global transcriptional regulator MgrA and the two-component system ArlRS. To identify additional regulators of norA, we screened a transposon library in strain Newman expressing the transcriptional fusion norA-lacZ for altered β-galactosidase activity. We identify a transposon insertion in fhuB, a gene that encodes a ferric hydroxamate uptake system permease, and propose that the norA transcription is iron responsive. In agreement with this observation, addition of FeCl3 repressed the induction of norA-lacZ, suggesting that bacterial iron uptake plays an important role in regulating norA transcription. In addition, a fur (ferric uptake regulator) deletion exhibited compromised norA transcription and reduced resistance to quinolone compared to the wild-type strain, indicating that fur functions as a positive regulator of norA. A putative Fur box identified in the promoter region of norA was confirmed by electrophoretic mobility shift and DNase I footprint assays. Finally, by employing a siderophore secretion assay, we reveal that NorA may contribute to the export of siderophores. Collectively, our experiments uncover some novel interactions between cellular iron level and norA regulation in S. aureus.
机译：金黄色葡萄球菌利用外排转运蛋白NorA抽出多种结构不同的药物，从而赋予了低水平的多药耐药性。尽管以前的研究表明该基因受全局转录调节因子MgrA和两组分系统ArlRS的控制，但尚未完全了解 norA 表达的调控。为了鉴定 norA 的其他调控子，我们筛选了表达转录融合 norA-lacZ 的β-半乳糖苷酶活性的纽曼菌株转座子文库。我们在 fhuB （一种编码异羟肟酸铁吸收系统通透酶的基因）中鉴定了转座子插入，并提出 norA 转录对铁有反应。与该观察结果一致，添加FeCl 3 抑制了 norA-lacZ 的诱导，表明细菌铁的摄取在调节 norA 转录。此外，与野生型菌株相比， fur （铁摄取调节剂）缺失表现出受损的 norA 转录并降低了对喹诺酮的抗性，表明 fur 充当 norA 的正调节剂。电泳迁移率变化和DNase I足迹分析证实了在 norA 启动子区域鉴定出的假定的Fur盒。最后，通过采用铁载体分泌测定，我们揭示了NorA可能有助于铁载体的输出。总的来说，我们的实验揭示了金黄色葡萄球菌中细胞铁水平与 norA 调控之间的一些新颖相互作用。

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