The ornibactin biosynthesis and transport genes of Burkholdetia cenocepacia are regulated by an extracytoplasmic function a factor which is a part of the fur regulon
The ornibactin biosynthesis and transport genes of Burkholdetia cenocepacia are regulated by an extracytoplasmic function a factor which is a part of the fur regulon
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DOI：
10.1128/jb.188.10.3631-3644.2006
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发表时间：
2006-05-01
影响因子：
3.2
通讯作者：
Thomas, Mark S.
中科院分区：
文献类型：
--
作者：
Agnoli, Kirsty;Lowe, Carolyn A.;Thomas, Mark S.
不能产生铁载体奥尼巴克丁的新洋葱伯克霍尔德杆菌突变体是在用 mini-Tn5Tp 诱变后获得的。这些突变体在缺铁条件下生长受到限制。在八个突变体中，转座子已整合到编码非核糖体肽合成酶的两个基因 orbI 和 orbJ 之一中。在另一个突变体中，转座子已插入位于 orbI 上游的开放阅读框 orbS 中。 orbS的多肽产物与铜绿假单胞菌胞质外功能(ECF)因子PvdS表现出高度相似性，但具有PvdS中不存在的约29个氨基酸的N端延伸。基于与 PvdS 依赖性启动子的相似性，在 ornibactin 基因簇内鉴定了三个预测的 OrbS 依赖性启动子。这些启动子的铁调节活性被证明需要 OrbS。发现 orbS 基因的转录受到铁调节的 sigma(70) 依赖性启动子的控制。该启动子（而非 OrbS 依赖性启动子）被证明是全局调节因子 Fur 抑制的目标。我们的结果表明，A cenocepacia 响应铁饥饿而产生 ornibactin 需要转录依赖于 Fur 调节的 ECF sigma 因子基因 orbS 的操纵子。还提出了奥尼巴汀生物合成的机制。
Burkholderia cenocepacia mutants that fail to produce the siderophore ornibactin were obtained following mutagenesis with mini-Tn5Tp. These mutants were shown to be growth restricted under conditions of iron depletion. In eight of the mutants, the transposon had integrated into one of two genes, orbI and orbJ, encoding nonribosomal peptide synthetases. In the other mutant, the transposon had inserted into an open reading frame, orbS, located upstream from orbI. The polypeptide product of orbS exhibits a high degree of similarity to the Pseudomonas aeruginosa extracytoplasmic function (ECF) a factor PvdS but possesses an N-terminal extension of approximately 29 amino acids that is not present in PvdS. Three predicted OrbS-dependent promoters were identified within the ornibactin gene cluster, based on their similarity to PvdS-dependent promoters. The iron-regulated activity of these promoters was shown to require OrbS. Transcription of the orbS gene was found to be under the control of an iron-regulated sigma(70)-dependent promoter. This promoter, but not the OrbS-dependent promoters, was shown to be a target for repression by the global regulator Fur. Our results demonstrate that production of ornibactin by A cenocepacia in response to iron starvation requires transcription of an operon that is dependent on the Fur-regulated ECF sigma factor gene orbS. A mechanism is also proposed for the biosynthesis of ornibactin.