Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48104, USA.
Mol Microbiol. 2010 Feb;75(4):900-9. doi: 10.1111/j.1365-2958.2009.07025.x. Epub 2010 Jan 13.
Iron acquisition mechanisms play an important role in the pathogenesis of many infectious microbes. In Bacillus anthracis, the siderophore petrobactin is required for both growth in iron-depleted conditions and for full virulence of the bacterium. Here we demonstrate the roles of two putative petrobactin binding proteins FatB and FpuA (encoded by GBAA5330 and GBAA4766 respectively) in B. anthracis iron acquisition and pathogenesis. Markerless deletion mutants were created using allelic exchange. The Delta fatB strain was capable of wild-type levels of growth in iron-depleted conditions, indicating that FatB does not play an essential role in petrobactin uptake. In contrast, Delta fpuA bacteria exhibited a significant decrease in growth under low-iron conditions when compared with wild-type bacteria. This mutant could not be rescued by the addition of exogenous purified petrobactin. Further examination of this strain demonstrated increased levels of petrobactin accumulation in the culture supernatants, suggesting no defect in siderophore synthesis or export but, instead, an inability of Delta fpuA to import this siderophore. Delta fpuA spores were also significantly attenuated in a murine model of inhalational anthrax. These results provide the first genetic evidence demonstrating the role of FpuA in petrobactin uptake.
铁获取机制在许多传染性微生物的发病机制中起着重要作用。在炭疽杆菌中，铁载体彼得巴辛对于细菌在缺铁条件下的生长和完全毒力都是必需的。在这里，我们证明了两个假定的彼得巴辛结合蛋白 FatB 和 FpuA（分别由 GBAA5330 和 GBAA4766 编码）在炭疽杆菌铁获取和发病机制中的作用。使用等位基因交换创建了无标记缺失突变体。Delta fatB 株在缺铁条件下的生长能力与野生型相当，表明 FatB 在彼得巴辛摄取中不起必需作用。相比之下，与野生型细菌相比，Delta fpuA 细菌在低铁条件下的生长显著下降。该突变体不能通过添加外源性纯化的彼得巴辛来挽救。对该菌株的进一步检查表明，培养上清液中的彼得巴辛积累水平增加，表明铁载体合成或输出没有缺陷，但相反，Delta fpuA 无法导入这种铁载体。Delta fpuA 孢子在吸入性炭疽的小鼠模型中也显著减毒。这些结果提供了第一个遗传证据，证明了 FpuA 在彼得巴辛摄取中的作用。
