Almirón M, Martínez M, Sanjuan N, Ugalde R A
Instituto de Investigaciones Biotecnológicas, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de General San Martín, Buenos Aires, Argentina.
Infect Immun. 2001 Oct;69(10):6225-30. doi: 10.1128/IAI.69.10.6225-6230.2001.
Brucella spp. are pathogenic bacteria that cause brucellosis, an animal disease which can also affect humans. Although understanding the pathogenesis is important for the health of animals and humans, little is known about virulence factors associated with it. In order for chronic disease to be established, Brucella spp. have developed the ability to survive inside phagocytes by evading cell defenses. It hides inside vacuoles, where it then replicates, indicating that it has an active metabolism. The purpose of this work was to obtain better insight into the intracellular metabolism of Brucella abortus. During a B. abortus genomic sequencing project, a clone coding a putative gene homologous to hemH was identified and sequenced. The amino acid sequence revealed high homology to members of the ferrochelatase family. A knockout mutant displayed auxotrophy for hemin, defective intracellular survival inside J774 and HeLa cells, and lack of virulence in BALB/c mice. This phenotype was overcome by complementing the mutant strain with a plasmid harboring wild-type hemH. These data demonstrate that B. abortus synthesizes its own heme and also has the ability to use an external source of heme; however, inside cells, there is not enough available heme to support its intracellular metabolism. It is concluded that ferrochelatase is essential for the multiplication and intracellular survival of B. abortus and thus for the establishment of chronic disease as well.
布鲁氏菌属是导致布鲁氏菌病的致病细菌，布鲁氏菌病是一种动物疾病，也会影响人类。尽管了解发病机制对动物和人类健康很重要，但对与之相关的毒力因子却知之甚少。为了引发慢性病，布鲁氏菌属已发展出通过逃避细胞防御在吞噬细胞内生存的能力。它隐藏在液泡内并在其中复制，这表明它具有活跃的新陈代谢。这项工作的目的是更深入地了解流产布鲁氏菌的细胞内代谢。在一个流产布鲁氏菌基因组测序项目中，鉴定并测序了一个编码与hemH同源的假定基因的克隆。氨基酸序列显示与铁螯合酶家族成员具有高度同源性。一个基因敲除突变体表现出血红素营养缺陷型，在J774和HeLa细胞内的细胞内存活存在缺陷，并且在BALB/c小鼠中缺乏毒力。通过用携带野生型hemH的质粒对突变菌株进行互补，克服了这种表型。这些数据表明，流产布鲁氏菌能合成自身的血红素，也有能力利用外部血红素来源；然而，在细胞内，没有足够的可用血红素支持其细胞内代谢。得出的结论是，铁螯合酶对流产布鲁氏菌的增殖和细胞内存活至关重要，因此对慢性病的发生也至关重要。
