Zhao Xiaoyu, Zhang Yixin, Ju Mohan, Yang Yang, Liu Haoqi, Qin Xiaohua, Xu Qingqing, Hao Min
Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.
Key Laboratory of Clinical Pharmacology of Antibiotics, National Heath Commission, Shanghai, China.
Microbiol Spectr. 2025 Feb 4;13(2):e0172824. doi: 10.1128/spectrum.01728-24. Epub 2024 Dec 31.
RamA is an intrinsic regulator in , belonging to the AraC family of transcription factors and conferring a multidrug resistance phenotype, especially for tetracycline-class antibiotics. The ATP-binding cassette transporters MlaFEDCB in bacteria play essential roles in functions essential for cell survival and intrinsic resistance to many antibiotics. We found deletion of resulted in a fivefold decrease in the transcriptional levels of the operon. After complementation with ramA, the transcriptional levels were comparable to those of wild-type strain. Furthermore, an electrophoretic mobility shift assay showed that RamA could bind to the promoter region of operon, which confirmed RamA is an activator of operon. The operon could mildly mediate resistance to the tetracycline family of antibiotics under RamA regulation. The MIC (minimum inhibitory concentration) of tigecycline decreased fourfold, and the MIC of doxycycline, minocycline, and eravacycline decreased twofold after -knockout. The - and -knockout strains exhibited greater sensitivity to sodium dodecyl sulfate (SDS)-EDTA than the wild-type. Growth of Δ cells was severely compromised in 0.25/0.5% SDS and 0.55 mM EDTA, and this sensitivity was restored by complementation with and . This study demonstrates that RamA can directly regulate the operon, thereby mediating resistance to tetracycline-class antibiotics, contributing to the stability of bacterial membranes in . We identified a novel signal pathway in which RamA mediates multidrug resistance of , leading to new ideas for the development of novel antimicrobial therapeutics, therefore deserving further comprehensive study.
Multidrug-resistant and extensively drug-resistant have emerged as significant global health concerns resulting in high mortality rates. Although previous research has investigated the maintenance of lipid asymmetry (Mla) pathway, the extent to which it mediates antimicrobial resistance in and the underlying upstream regulatory mechanisms remain unclear. In this study, we sought to determine at the molecular level how the AraC-type global regulator RamA directly regulates mlaFEDCB, which mediates resistance to tetracycline-class antibiotics and the stability of bacterial membranes in .
RamA是[细菌名称]中的一种内在调节因子，属于AraC转录因子家族，赋予多药耐药表型，尤其是对四环素类抗生素。细菌中的ATP结合盒转运蛋白MlaFEDCB在细胞存活所必需的功能以及对多种抗生素的内在抗性中起重要作用。我们发现[基因名称]的缺失导致[基因名称]操纵子的转录水平下降了五倍。用ramA互补后，转录水平与野生型菌株相当。此外，电泳迁移率变动分析表明RamA可以结合到[基因名称]操纵子的启动子区域，这证实RamA是[基因名称]操纵子的激活剂。在RamA调控下，[基因名称]操纵子可以轻度介导对四环素类抗生素的抗性。[基因名称]敲除后，替加环素的最低抑菌浓度（MIC）降低了四倍，强力霉素、米诺环素和依拉环素的MIC降低了两倍。[基因名称]和[基因名称]敲除菌株对十二烷基硫酸钠（SDS）-乙二胺四乙酸（EDTA）的敏感性高于野生型。Δ[基因名称]细胞在0.25/0.5% SDS和0.55 mM EDTA中生长严重受损，这种敏感性通过用[基因名称]和[基因名称]互补得以恢复。本研究表明，RamA可以直接调节[基因名称]操纵子，从而介导对四环素类抗生素的抗性，有助于[细菌名称]中细菌膜的稳定性。我们鉴定了一条新的信号通路，其中RamA介导[细菌名称]的多药耐药性，为新型抗菌治疗药物的开发带来了新的思路，因此值得进一步全面研究。
耐多药和广泛耐药的[细菌名称]已成为全球重大的健康问题，导致高死亡率。尽管先前的研究已经调查了维持脂质不对称（Mla）途径，但它在[细菌名称]中介导抗菌抗性的程度以及潜在的上游调控机制仍不清楚。在本研究中，我们试图在分子水平上确定AraC型全局调节因子RamA如何直接调节mlaFEDCB，后者介导对四环素类抗生素的抗性以及[细菌名称]中细菌膜的稳定性。
