IRON UPTAKE AS A VIRULENCE FACTOR IN PATHOGENIC VIBRIOS

拟议研究的长期目标是详细分析 毒力相关的性质，质粒介导的铁摄取， 在许多侵袭性败血症的发病机制中起重要作用 人类和家畜的疾病。我们的模型系统是鱼类病原体 鳗弧菌引起晚期出血性败血症。这 细菌具有质粒介导的铁摄取系统， 是其毒力库的重要组成部分。这一特点 质粒介导的毒力决定簇使其成为一个非常有吸引力的模型， 研究宿主与细菌的相互作用。在过去的授予期内， 描述了这个系统的基本组成部分：铁载体 运输蛋白OM 2和P40，以及调控元件 控制其生物合成。具体的机制，这些 组分调节铁的吸收过程，从而在V. 拟开展的调查将进一步阐明鳗属的情况。的 实现这些目标的具体目标是：1）确定遗传 决定簇及其编码的多肽参与的生物合成 铁载体angiibactin。我们将结合基因和 物理方法来剖析anguibactin的生物合成途径。2)到 表征铁转运到细胞胞质溶胶中的机制， 研究P40、OM 2和ORFs 1的产物所起的作用， 2也编码在铁转运区。3)要定义的性质 铁吸收基因表达的正调控。 anguillarum的转录调控因子AngR和TAF。4)以限定 铁对铁表达负调节的本质 运输基因我们已经鉴定了P40-OM 2中编码的反义RNA， 在富铁条件下诱导的基因间区，伴随 P40和OM 2 mRNA的合成减少。我们的证据 表明这种反义RNA可能在铁调节中起作用， P40和OM 2铁转运基因在鳗弧菌中的表达。我们 将决定这是否是铁抑制的中心机制 或者它是否是一个更复杂的 调节电路，也可以包括毛皮样元件。总之， 这种质粒介导的铁吸收系统的分子研究应该 提供了有用的信息，在两个基本方面的质粒介导的 铁摄取及其作为细菌毒力因子作用。

The long term objective of the proposed research is the detailed analysis of a virulence associated property, plasmid-mediated iron uptake, which plays an important role in the pathogenesis of many invasive septicemic diseases of man and domestic animals. Our model system is the fish pathogen Vibrio anguillarum which causes a terminal hemorrhagic septicemia. This bacterium possesses a plasmid-mediated iron uptake system that is an important component of its virulence repertoire. The features of this plasmid-mediated virulence determinant makes it a very attractive model to study host-bacterial interactions. In the past granting period we have characterized the essential components of this system: the siderophore anguibactin; the transport proteins OM2 and P40, and regulatory elements controlling their biosynthesis. The specific mechanisms by which these components regulate the process of iron uptake, and thus virulence, in V. anguillarum will be further elucidated by the proposed investigation. The specific aims to achieve these objectives are: 1) To identify the genetic determinants and their encoded polypeptides involved in the biosynthesis of the siderophore anguibactin. We will use a combination of genetic and physical methods to dissect the biosynthetic pathway of anguibactin. 2) To characterize the mechanism of transport of iron into the cell cytosol and investigation of the role played by P40, OM2 and the products of ORFs 1 and 2 also encoded in the iron transport region. 3) To define the nature of the positive regulation of the expression of iron-uptake genes in V. anguillarum by the transcriptional regulators AngR and TAF. 4) to define the nature of the negative regulation by iron of the expression of iron transport genes. We have identified an antisense RNA encoded in the P40-OM2 intergenic region that is induced under iron-rich conditions, concomitant with a decrease in the synthesis of the P40 and OM2 mRNAs. Our evidence indicates that this antisense RNA may play a role in the iron regulation of the expression of the P40 and OM2 iron transport genes in V.anguillarum. We will determine whether this is the central mechanism of repression of iron transport in this bacterium or whether it is part of a more complex regulatory circuit that may also include Fur-like elements. In summary, the molecular studies of this plasmid-mediated iron-uptake system should provide useful information in both the basic aspects of plasmid-mediated iron uptake and its role as a bacterial virulence factor.