Dorsey Caleb W, Tomaras Andrew P, Connerly Pamela L, Tolmasky Marcelo E, Crosa Jorge H, Actis Luis A
Department of Microbiology, 40 Pearson Hall, Miami University, Oxford, OH 45056, USA.
Department of Biological Science, California State University Fullerton, Fullerton, CA 92834-6850, USA.
Microbiology (Reading). 2004 Nov;150(Pt 11):3657-3667. doi: 10.1099/mic.0.27371-0.
The Acinetobacter baumannii type strain, ATCC 19606, secretes acinetobactin, a catechol siderophore highly related to the iron chelator anguibactin produced by the fish pathogen Vibrio anguillarum (Listonella anguillarum). This paper reports the initial characterization of the genes and gene products involved in the acinetobactin-mediated iron-acquisition process. Insertional mutagenesis resulted in the isolation of several derivatives whose ability to grow in medium containing the iron chelator 2,2'-dipyridyl was affected. One of the insertions disrupted a gene encoding a predicted outer-membrane protein, named BauA, highly similar to FatA, the receptor for ferric anguibactin. Immunological relatedness of BauA with FatA was confirmed by Western blot analysis. Another transposon insertion was mapped to a gene encoding a protein highly similar to FatD, the permease component of the anguibactin transport system. Further DNA sequencing and nucleotide sequence analysis revealed that these A. baumannii 19606 genes are part of a polycistronic locus that contains the bauDCEBA ORFs. While the translation products of bauD, -C, -B and -A are highly related to the V. anguillarum FatDCBA iron-transport proteins, the product of bauE is related to the ATPase component of Gram-positive ATP-binding cassette (ABC) transport systems. This entire locus is flanked by genes encoding predicted proteins related to AngU and AngN, V. anguillarum proteins required for the biosynthesis of anguibactin. These protein similarities, as well as the structural similarity of anguibactin and acinetobactin, suggested that these two siderophores could be utilized by both bacterial strains, a possibility that was confirmed by siderophore utilization bioassays. Taken together, these results demonstrate that these pathogens, which cause serious infections in unrelated hosts, express very similar siderophore-mediated iron-acquisition systems.
鲍曼不动杆菌模式菌株ATCC 19606分泌鲍曼不动杆菌素，这是一种儿茶酚型铁载体，与鱼类病原菌鳗弧菌（鳗弧菌属）产生的铁螯合剂鳗弧菌素高度相关。本文报道了参与鲍曼不动杆菌素介导的铁摄取过程的基因及其产物的初步特征。插入诱变导致分离出几种衍生物，其在含有铁螯合剂2,2'-联吡啶的培养基中生长的能力受到影响。其中一个插入突变破坏了一个编码预测外膜蛋白的基因，命名为BauA，它与鳗弧菌素铁载体的受体FatA高度相似。通过蛋白质免疫印迹分析证实了BauA与FatA的免疫相关性。另一个转座子插入定位到一个编码与FatD高度相似的蛋白质的基因，FatD是鳗弧菌素转运系统的通透酶成分。进一步的DNA测序和核苷酸序列分析表明，这些鲍曼不动杆菌19606基因是一个多顺反子位点的一部分，该位点包含bauDCEBA开放阅读框。虽然bauD、-C、-B和-A的翻译产物与鳗弧菌的FatDCBA铁转运蛋白高度相关，但bauE的产物与革兰氏阳性ATP结合盒（ABC）转运系统的ATP酶成分相关。整个位点两侧是编码与鳗弧菌AngU和AngN相关的预测蛋白的基因，AngU和AngN是鳗弧菌素生物合成所需的蛋白。这些蛋白质的相似性，以及鳗弧菌素和鲍曼不动杆菌素的结构相似性，表明这两种铁载体可能被两种细菌菌株利用，铁载体利用生物测定证实了这一可能性。综上所述，这些结果表明，这些在不相关宿主中引起严重感染的病原菌表达非常相似的铁载体介导的铁摄取系统。
