Genetic organization of an Acinetobacter baumannii chromosomal region harbouring genes related to siderophore biosynthesis and transport
Genetic organization of an Acinetobacter baumannii chromosomal region harbouring genes related to siderophore biosynthesis and transport
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DOI：
10.1099/mic.0.26204-0
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发表时间：
2003-05-01
期刊：
影响因子：
2.8
通讯作者：
Actis, LA
中科院分区：
文献类型：
--
作者：
Dorsey, CW;Tolmasky, ME;Actis, LA
鲍氏不动杆菌8399临床分离株分泌二羟基苯甲酸（DHBA）和高亲和力的儿茶酚铁载体，这是从其他细菌铁螯合剂已经表征不同。用肠杆菌素缺陷型大肠杆菌菌株进行互补试验，分离出一个含有A. DHBA生物合成和活化所需的鲍曼不动杆菌8399基因。因此，克隆的片段含有dhbACEB多顺反子操纵子，其编码预测的蛋白质，所述蛋白质与从胆酸生物合成DHBA所需的几种细菌蛋白质高度相似。在dhbACEB位点旁边发现了编码与大肠杆菌Fes和枯草芽孢杆菌DhbF蛋白相关的推导蛋白的基因，以及推定的鼠疫耶尔森菌磷酸泛酰巯基乙胺基转移酶，所有这些基因都参与了在其他细菌中儿茶酚铁载体的组装和利用。这个A.鲍曼不动杆菌8399基因簇还含有OM 73、p45和p114预测的编码可能涉及三价铁载体复合物转运的蛋白质的基因。p114和p45基因的推导产物是分别属于RND和MFS外排泵蛋白的推定膜蛋白。有趣的是，P45与参与肠杆菌素分泌的大肠杆菌P43（EntS）蛋白高度相关。虽然P114与其他参与抗生素耐药性的细菌外排泵蛋白相似，但其在该A.鲍曼不动杆菌8399位点与其它细菌中描述的不同。om 73的产物是一种由毛皮和铁调节的表面暴露的外膜蛋白。这些特征以及预测的TonB盒的存在及其与其他铁载体受体的高度相似性表明OM 73在A.鲍曼不动杆菌8399。184 nt的om 73-p114基因间区包含启动子元件，可以驱动这些差异转录基因的表达，所有这些基因都非常接近几乎完美的Fur盒。这种安排解释了铁和毛皮调节om 73的表达，并提供了强有力的证据，为p114的表达类似的调节。
The Acinetobacter baumannii 8399 clinical isolate secretes dihydroxybenzoic acid (DHBA) and a high-affinity catechol siderophore, which is different from other bacterial iron chelators already characterized. Complementation assays with enterobactin-deficient Escherichia coli strains led to the isolation of a cosmid clone containing A. baumannii 8399 genes required for the biosynthesis and activation of DHBA. Accordingly, the cloned fragment harbours a dhbACEB polycistronic operon encoding predicted proteins highly similar to several bacterial proteins required for DHBA biosynthesis from chorismic acid. Genes encoding deduced proteins related to the E coli Fes and the Bacillus subtilis DhbF proteins, and a putative Yersinia pestis phosphopantetheinyl transferase, all of them involved in the assembly and utilization of catechol siderophores in other bacteria, were found next to the dhbACEB locus. This A. baumannii 8399 gene cluster also contained the om73, p45 and p114 predicted genes encoding proteins potentially involved in transport of ferric siderophore complexes. The deduced products of the p 114 and p45 genes are putative membrane proteins that belong to the RND and MFS efflux pump proteins, respectively. Interestingly, P45 is highly related to the E coli P43 (EntS) protein that participates in the secretion of enterobactin. Although P114 is similar to other bacterial efflux pump proteins involved in antibiotic resistance, its genetic arrangement within this A. baumannii 8399 locus is different from that described in other bacteria. The product of om73 is a Fur- and iron-regulated surface-exposed outer-membrane protein. These characteristics together with the presence of a predicted TonB box and its high similarity to other siderophore receptors indicate that OM73 plays such a role in A. baumannii 8399. The 184 nt om73-p114 intergenic region contains promoter elements that could drive the expression of these divergently transcribed genes, all of which are in close proximity to almost perfect Fur boxes. This arrangement explains the iron- and Fur-regulated expression of om73, and provides strong evidence for a similar regulation for the expression of p114.