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首页> 外文期刊>Infection and immunity >Two TonB Systems in Actinobacillus pleuropneumoniae: Their Roles in Iron Acquisition and Virulence
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Two TonB Systems in Actinobacillus pleuropneumoniae: Their Roles in Iron Acquisition and Virulence

机译：胸膜肺炎放线杆菌中的两个TonB系统：在铁的获取和毒力中的作用

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Iron acquisition in vivo by Actinobacillus pleuropneumoniae depends upon a functional TonB system. Tonpitak et al. (W. Tonpitak, S. Thiede, W. Oswald, N. Baltes, and G.-F. Gerlach, Infect. Immun. >68:1164-1170, 2000) have described one such system, associated with tbpBA encoding the transferrin receptor, and here we report a second, termed tonB2. This gene cluster (exbB2-exbD2-tonB2) is highly homologous to those in other Pasteurellaceae, unlike the earlier system described (now termed tonB1), suggesting that it is the indigenous system for this organism. Both tonB2 and tonB1 are upregulated upon iron restriction. TonB2, but not TonB1, was found to be essential for growth in vitro when the sole source of iron was hemin, porcine hemoglobin, or ferrichrome. In the case of iron provided as iron-loaded porcine transferrin, neither tonB mutant was viable. The tonB1 phenotype could be explained by a polar effect of the mutation on transcription of downstream tbp genes. We propose that TonB2 is crucial for the acquisition of iron provided in this form, interacting with accessory proteins of the TonB1 system that have been demonstrated to be necessary by Tonpitak et al. TonB2 appears to play a much more important role in A. pleuropneumoniae virulence than TonB1. In an acute porcine infection model, the tonB2 mutant was found to be highly attenuated, while the tonB1 mutant was not. We hypothesize that acquisition of the tonB1-tbp gene cluster confers a biological advantage through its capacity to utilize transferrin-iron but that TonB1 itself plays little or no part in this process.
机译：胸膜肺炎放线杆菌在体内的铁吸收取决于功能性TonB系统。 Tonpitak等。 （W. Tonpitak，S。Thiede，W。Oswald，N。Baltes和G.-F. Gerlach，Infect。Immun。> 68： 1164-1170，2000）描述了一种这样的系统，与编码转铁蛋白受体的 tbpBA 相关，这里我们报告第二种，称为 tonB2 。该基因簇（ exbB2 - exbD2 - tonB2 ）与其他 Pasteurellaceae 中的基因簇高度同源所描述的系统（现在称为 tonB1 ），表明这是该生物体的本地系统。铁限制后， tonB2 和 tonB1 均被上调。当铁的唯一来源是血红素，猪血红蛋白或铁铬铁时，发现TonB2（而非TonB1）对于体外生长至关重要。在铁作为载铁猪转铁蛋白的情况下， tonB 突变体均不可行。 tonB1 表型可以用突变对下游 tbp 基因转录的极性影响来解释。我们建议TonB2对于以这种形式提供的铁的获取至关重要，它与Tonpitak等人已证明必需的TonB1系统的辅助蛋白相互作用。 TonB2在 A中似乎起着更为重要的作用。胸膜肺炎的毒力比TonB1高。在急性猪感染模型中，发现 tonB2 突变体高度减毒，而 tonB1 突变体却没有。我们假设 tonB1-tbp 基因簇的获得通过其利用转铁蛋白铁的能力而赋予了生物学优势，但TonB1本身在该过程中几乎没有或没有任何作用。

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