Biosynthetic and regulatory elements involved in the production of the siderophore vanchrobactin in Vibrio anguillarum
Biosynthetic and regulatory elements involved in the production of the siderophore vanchrobactin in Vibrio anguillarum
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DOI：
10.1099/mic.0.2008/016618-0
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发表时间：
2008-05-01
期刊：
影响因子：
2.8
通讯作者：
Lemos, Manuel L.
中科院分区：
文献类型：
--
作者：
Balado, Miguel;Osorio, Carlos R.;Lemos, Manuel L.
一些鳗弧菌菌株产生一种名为vanchrobactin的儿茶酚型铁载体，其生物合成途径尚未完全阐明。除了先前描述的基因vabA，vabC，vabB，vabE，vabF，vabS和vabH，在本研究中，我们已经确定了编码DAHP（3-脱氧-D-阿拉伯庚酮糖酸-7-磷酸）合成酶（vabG），磷酸泛黄素转移酶（vabD），赖氨酸受体家族转录调节因子（vabR）和推定的铁载体受体（MA）的基因。影响vabG或vabD的缺失大大降低了铁限制条件下的生长，而vabR的缺失没有显着的影响，vabD突变体中的Vanchrobactin生产被废除，而vabG突变体保留了残余的vanchrobactin生产能力。逆转录酶介导的PCR表明，这11个基因簇被组织成6个铁调控的转录单位。转录lacZ融合表明，铁吸收调节（Fur）蛋白是这些基因的主要铁响应调节。有趣的是，vabG基因是强烈的铁抑制，但毛皮是不是必不可少的这种镇压。此外，从vabG启动子的最大表达仅在vabR的完整拷贝的存在下实现。在vabB突变体中和添加万古菌素的情况下，对fvtA：：lacZ融合物的β-半乳糖苷酶活性的分析表明，铁-万古菌素依赖性激活剂在fvtA-vabD操纵子的转录中起着积极的调节作用。这种可能性是加强了预测的AraC框上游的fvtA的存在。我们建议，vanchrobactin的生物合成受到一个复杂的调节电路，旨在调整vanchrobactin生产的维持铁稳态鳗弧菌。
Some Vibrio anguillarum strains produce a catechol-type siderophore named vanchrobactin, whose biosynthetic pathway has not been completely elucidated. In addition to the previously described genes vabA, vabC, vabB, vabE, vabF, vabS and vabH, in the present study we have identified the genes encoding a DAHP (3-deOxy-D-arabino-heptulosonate-7-phosphate) synthetase (vabG), a phosphopantheteinyl transferase (vabD), a LysR-family transcriptional regulator (vabR) and a putative siderophore receptor (MA). A deletion affecting vabG or vabD greatly reduced growth under iron-limiting conditions, whereas deletion of vabR did not have significant effects, Vanchrobactin production was abolished in the vabD mutant, whereas the vabG mutant retained a residual vanchrobactin production ability. Reverse transcriptase-mediated PCR indicated that this 11-gene cluster is organized into six iron-regulated transcriptional units. Transcriptional lacZ fusions demonstrated that the ferric uptake regulator (Fur) protein is the main iron-responsive regulator of these genes. Interestingly, the vabG gene was strongly iron-repressed, but Fur was not essential for this repression. In addition, the maximal expression from the vabG promoter was achieved only in the presence of an intact copy of vabR. Analysis of the beta-galactosidase activities of a fvtA: : lacZ fusion in a vabB mutant and in the presence of added vanchrobactin suggested that a ferric-vanchrobactin-dependent activator plays a positive regulatory role in transcription of the fvtA-vabD operon. This possibility is reinforced by the presence of a predicted AraC box upstream of fvtA. We propose that vanchrobactin biosynthesis is subjected to a complex regulatory circuitry aimed at adjusting vanchrobactin production for the maintenance of iron homeostasis in V anguillarum.