镓通过铁摄取调节因子抑制PVD合成干扰铜绿假单胞菌铁代谢的机制研究

镓是常见抗菌金属离子，能抑制铜绿假单胞菌转录起始因子(pvdS)的启动，阻碍铁载体(PVD)表达合成，干扰细菌铁代谢，但其机制尚不明确。铁摄取调节因子(Fur)对维持细菌铁代谢至关重要，它通过与铁离子形成复合体，与靶基因pvdS启动子结合，发挥调控作用。前期发现Fur可与镓离子结合，但能否形成稳定的复合物并抑制pvdS表达尚不清楚。基于Fur结构特征，镓与铁的化学相似性，推测镓可与Fur形成稳定复合体，靶向抑制pvdS启动及PVD合成。为验证该假说，首先拟采用荧光光谱法和凝胶电泳迁移率评价镓离子与Fur结合的稳定性及该复合物与DNA的结合能力，再通过体内外抗菌实验，观察铜绿假单胞菌野生株与fur突变株在镓离子作用下靶基因pvdS表达及PVD变化，以确证镓离子通过Fur-pvdS-PVD途径干扰铜绿假单胞菌铁代谢，发挥抗菌作用。本课题对深入了解镓离子抗菌机制、寻找有效的抑菌靶点具有重要价值。

Gallium has great antibacterial activity against various pathogens common in wound infections. Gallium ions exhibit an antibacterial effect against Pseudomonas Aeruginosa through inhibiting the expression of transcription factor (pvdS) and reducing the content of pyoverdine (PVD), and interfering with iron metabolism, which mechanism is unclear yet. Bacteria have a global iron regulation system, which core is ferric uptake regulator (Fur). A complex formed by Fur and iron can bind with the specific region of DNA which control the expression of iron carriers and other related proteins according to the iron supply, to achieve the balance of iron metabolism. Based on the chemical similarity between Ga3+ and Fe3+, it is speculated that Ga3+ exerts interferential effect by inhibiting expression of pvdS and synthesis of PVD through the way of forming a complex with Fur. Therefore, this study first intends to evaluate the binding ability of Ga3+ with Fur and the complex with DNA by fluorescence spectrometry and electrophoretic mobility shift assay. In addition, in vitro and in vivo antibacterial experiments were conducted to study the changes of target gene pvdS expression and PVD synthesis of wild-type and fur mutant Pseudomonas Aeruginosa strain exposed to gallium ions, which aim to verify that gallium ions play an interferential effect to iron metabolism through Fur-pvdS-PVD pathway. This project is expected to provide evidence for clarifying the antibacterial mechanism of gallium ions, and provide experimental basis for further research.