Identification of a membrane-bound transcriptional regulator that links chitin and natural competence in Vibrio cholerae.
Identification of a membrane-bound transcriptional regulator that links chitin and natural competence in Vibrio cholerae.
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DOI：
10.1128/mbio.01028-13
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发表时间：
2014-01-28
期刊：
影响因子：
6.4
通讯作者：
Camilli A
中科院分区：
文献类型：
--
作者：
Dalia AB;Lazinski DW;Camilli A
霍乱弧菌在甲壳质上生长时自然具有活性。众所周知，能力的主要调节因子 TfoX 的表达是由几丁质控制的。然而，这种对甲壳素的需求背后的分子机制仍不清楚。在本研究中，我们鉴定并表征了一种膜结合转录调节因子，该调节因子可以正向调节小 RNA (sRNA) TfoR，从而在转录后增强 tfoX 翻译。我们通过电泳迁移率变动分析以及该系统在大肠杆菌中的异源表达证明了 tfoR 启动子的这种调节是直接的。该转录调节因子最近被独立鉴定并命名为“TfoS”（S. Yamamoto 等人，Mol. Microbiol.，出版中，doi:10.1111/mmi.12462）。使用 TfoS 的组成型活性形式，我们证明该调节剂的活性足以在缺乏几丁质的情况下提高霍乱弧菌的能力。此外，TfoS 包含一个大的周质结构域，我们假设它与几丁质相互作用以调节 TfoS 活性。在异源宿主大肠杆菌中，我们证明几丁质寡糖足以激活 tfoR 启动子处的 TfoS 活性。总的来说，这些数据将 TfoS 描述为一种新型几丁质感应转录调节因子，代表了几丁质与霍乱弧菌自然能力之间的直接联系。天然感受态细菌可以从环境中摄取外源DNA，并通过同源重组将其整合到其基因组中。这种吸收外源 DNA 的能力是多种细菌所共有的，并且是一种获取新基因以增强生物体适应性的机制。弧菌科的一些成员在甲壳质上生长时会自然而然地变得有能力。然而，目前还缺乏对几丁质如何激活能力的分子理解。在这里，我们鉴定了一种新型膜结合转录调节因子，它是人类病原体霍乱弧菌自然转化所需的。我们证明该调节剂感知几丁质寡糖以激活能力级联，从而揭示了该弧菌物种中几丁质和自然能力之间的分子联系。
Vibrio cholerae is naturally competent when grown on chitin. It is known that expression of the major regulator of competence, TfoX, is controlled by chitin; however, the molecular mechanisms underlying this requirement for chitin have remained unclear. In the present study, we identify and characterize a membrane-bound transcriptional regulator that positively regulates the small RNA (sRNA) TfoR, which posttranscriptionally enhances tfoX translation. We show that this regulation of the tfoR promoter is direct by performing electrophoretic mobility shift assays and by heterologous expression of this system in Escherichia coli. This transcriptional regulator was recently identified independently and was named “TfoS” (S. Yamamoto et al., Mol. Microbiol., in press, doi:10.1111/mmi.12462). Using a constitutively active form of TfoS, we demonstrate that the activity of this regulator is sufficient to promote competence in V. cholerae in the absence of chitin. Also, TfoS contains a large periplasmic domain, which we hypothesized interacts with chitin to regulate TfoS activity. In the heterologous host E. coli, we demonstrate that chitin oligosaccharides are sufficient to activate TfoS activity at the tfoR promoter. Collectively, these data characterize TfoS as a novel chitin-sensing transcriptional regulator that represents the direct link between chitin and natural competence in V. cholerae. Naturally competent bacteria can take up exogenous DNA from the environment and integrate it into their genome by homologous recombination. This ability to take up exogenous DNA is shared by diverse bacterial species and serves as a mechanism to acquire new genes to enhance the fitness of the organism. Several members of the family Vibrionaceae become naturally competent when grown on chitin; however, a molecular understanding of how chitin activates competence is lacking. Here, we identify a novel membrane-bound transcriptional regulator that is required for natural transformation in the human pathogen Vibrio cholerae. We demonstrate that this regulator senses chitin oligosaccharides to activate the competence cascade, thus, uncovering the molecular link between chitin and natural competence in this Vibrio species.