Metal-dependent repression of siderophore and biofilm formation in Actinomyces naeslundii
Metal-dependent repression of siderophore and biofilm formation in Actinomyces naeslundii
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DOI：
10.1111/j.1574-6968.2007.00888.x
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发表时间：
2007-10-01
影响因子：
2.1
通讯作者：
Bergeron, Lori
中科院分区：
文献类型：
--
作者：
Moelling, Cas;Oberschlacke, Ross;Bergeron, Lori
内氏放线菌是口腔的先驱，在牙齿表面形成生物膜。大多数细菌需要铁来生存，在病原菌中，铁的可获得性调节毒力基因的表达。金属依赖的抑制因子控制着包括铁载体在内的参与金属转运和吸收的基因表达。铁载体是细菌和真菌合成的获取铁的小分子。研究人员在奈氏拟线虫基因组中搜索了一种编码金属依赖抑制物的基因。鉴定了放线菌金属依赖阻遏因子或AMDR。检测AMDR蛋白与铁载体摄取编码基因(sid基因)的启动子序列结合的能力。凝胶位移分析表明，AMDR与sid基因启动子序列结合。在作者的模型中，当铁可用时，AMDR与sid启动子结合，并抑制sid基因的表达。为了进一步探讨AMDR的作用，我们构建了一株AMDR缺陷的内氏假丝酵母菌株，并对其生物膜的形成和铁载体的产生进行了评价。当培养液中的铁被去除后，奈氏假单胞菌会增加生物膜和铁载体的产量。然而，AMDR缺陷的内氏假丝酵母对生长介质中的金属离子浓度不那么敏感。
Actinomyces naeslundii is a pioneer of the oral cavity and forms a biofilm on the tooth's surface. Most bacteria require iron for survival and in pathogenic bacteria iron availability regulates virulence gene expression. Metal-dependent repressors control gene expression involved in metal transport and uptake including siderophores. Siderophores are small molecules synthesized by bacteria and fungi to acquire iron. The A. naeslundii genome was searched for a gene encoding a metal-dependent repressor. Actinomyces metal-dependent repressor or amdR was identified. The AmdR protein was examined for its ability to bind to the promoter sequence of a gene encoding the siderophore uptake (sid gene). According to gel shift assays, AmdR binds to the sid gene promoter sequences. In the authors' model, when iron is available AmdR binds to the sid promoter and represses sid gene expression. To further explore the role of AmdR, an amdR-defective strain of A. naeslundii was constructed and biofilm formation and siderophore production were evaluated. When iron is removed from the medium A. naeslundii increases biofilm and siderophore production. However, amdR-defective A. naeslundii is less sensitive to metal ion concentrations in the growth medium.