The regulatory network of natural competence and transformation of Vibrio cholerae.
The regulatory network of natural competence and transformation of Vibrio cholerae.
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DOI：
10.1371/journal.pgen.1002778
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发表时间：
2012
期刊：
影响因子：
4.5
通讯作者：
Blokesch M
中科院分区：
文献类型：
--
作者：
Lo Scrudato M;Blokesch M
人类病原体霍乱弧菌是一种常见于河流、湖泊、河口和沿海地区的水生细菌。在这些环境水库中，细菌通常与浮游动物有关，更具体地说，与它们的几丁质外骨骼有关。在这种几丁质表面上生长后，霍乱弧菌启动了一个称为“遗传转化的天然能力”的发育程序。天然转化能力是细菌基因水平转移的一种方式，有助于细菌基因组的维持和进化。在这项研究中，我们调查了感受态基因表达在这种生物体在单细胞水平。我们提供的证据表明，在均匀诱导条件下，大多数细胞表达感受态基因。一个更异质性的表达模式上观察到几丁质表面。我们假设，这是由于周围的甲壳素表面的异质性，这可能会有很大的变化，相对于甲壳素降解产物和自诱导剂的情况下，这些分子有助于基于碳分解代谢物阻遏和群体感应途径的感受态诱导，分别。因此，我们研究了这两个信号通路的贡献，以自然的能力，详细使用自然转化试验，转录报告融合，定量RT-PCR，和免疫检测蛋白质水平的Western印迹分析。结果表明，所有测试的感受态基因都依赖于转化调节因子TfoX。此外，细胞内cAMP水平在自然转化中起主要作用。最后，我们证明，只有少数参与自然转化的基因以群体感应依赖的方式进行调节，这些基因决定周围DNA的命运。最后，我们得出了一个模型的调控电路几丁质诱导的自然能力V.霍乱弧菌。 人类病原体霍乱弧菌是一种常见于河流、河口和沿海地区的水生细菌。在这个环境生态位中，细菌通常与浮游动物的几丁质外骨骼联系在一起。在这些几丁质表面的定殖后，霍乱弧菌开启了一种称为遗传转化天然能力的发育程序。天然转化能力是一种水平基因转移模式，允许细菌获得来自游离DNA的新基因，这些游离DNA由同一栖息地内的其他成员释放。进化的后果可能是，细菌受体变得更好地适应其环境生态位，或者在最坏的情况下，更致病的人。这项研究的结果表明，在最佳条件下，大多数细胞内的霍乱弧菌人口表达能力基因。然而，在水生环境中，不同的生态因素的组合可能会导致异质性的感受态表型。因此，我们研究了细胞外和细胞内信号分子在感受态诱导中的作用。这份报告说明，至少需要三个相互关联的信号级联的感受态诱导，这是基于细菌的代谢和群体行为。
The human pathogen Vibrio cholerae is an aquatic bacterium frequently encountered in rivers, lakes, estuaries, and coastal regions. Within these environmental reservoirs, the bacterium is often found associated with zooplankton and more specifically with their chitinous exoskeleton. Upon growth on such chitinous surfaces, V. cholerae initiates a developmental program termed “natural competence for genetic transformation.” Natural competence for transformation is a mode of horizontal gene transfer in bacteria and contributes to the maintenance and evolution of bacterial genomes. In this study, we investigated competence gene expression within this organism at the single cell level. We provide evidence that under homogeneous inducing conditions the majority of the cells express competence genes. A more heterogeneous expression pattern was observable on chitin surfaces. We hypothesize that this was the case due to the heterogeneity around the chitin surface, which might vary extensively with respect to chitin degradation products and autoinducers; these molecules contribute to competence induction based on carbon catabolite repression and quorum-sensing pathways, respectively. Therefore, we investigated the contribution of these two signaling pathways to natural competence in detail using natural transformation assays, transcriptional reporter fusions, quantitative RT–PCR, and immunological detection of protein levels using Western blot analysis. The results illustrate that all tested competence genes are dependent on the transformation regulator TfoX. Furthermore, intracellular cAMP levels play a major role in natural transformation. Finally, we demonstrate that only a minority of genes involved in natural transformation are regulated in a quorum-sensing-dependent manner and that these genes determine the fate of the surrounding DNA. We conclude with a model of the regulatory circuit of chitin-induced natural competence in V. cholerae. The human pathogen Vibrio cholerae is an aquatic bacterium often encountered in rivers, estuaries, and coastal regions. Within this environmental niche, the bacterium often associates with the chitinous exoskeleton of zooplankton. Upon colonization of these chitinous surfaces, V. cholerae switches on a developmental program known as natural competence for genetic transformation. Natural competence for transformation is a mode of horizontal gene transfer that allows bacteria to acquire new genes derived from free DNA, which is released by other members within the same habitat. The evolutionary consequences could be that the bacterial recipient becomes better adapted to its environmental niche or, in a worst-case scenario, more pathogenic for man. The results of this study show that, under optimal conditions, the majority of cells within a V. cholerae population express competence genes. However, in an aquatic environment, a combination of different ecological factors might lead to heterogeneity in the competence phenotype. Therefore, we investigated the role of extracellular and intracellular signaling molecules with respect to competence induction. This report illustrates that at least three interconnected signaling cascades are required for competence induction, which are based on bacterial metabolism and group behavior.
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