c-di-GMP heterogeneity is generated by the chemotaxis machinery to regulate flagellar motility.
c-di-GMP heterogeneity is generated by the chemotaxis machinery to regulate flagellar motility.
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DOI：
10.7554/elife.01402
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发表时间：
2013-12-17
期刊：
影响因子：
7.7
通讯作者：
Miller SI
中科院分区：
文献类型：
--
作者：
Kulasekara BR;Kamischke C;Kulasekara HD;Christen M;Wiggins PA;Miller SI
个体细胞异质性在种群中很常见，尽管其分子基础在很大程度上是未知的。以前，使用基于FRET的显微镜，我们观察到细胞c-di-GMP水平的异质性。在这项研究中，我们发现铜绿假单胞菌中c-di-GMP的异质性是由细胞分裂后分离的一种特定的磷酸二酯酶促进的。我们发现，这种磷酸二酯酶的亚细胞定位和c-di-GMP水平的降低依赖于趋化机制的组氨酸激酶成分CHEA及其磷酸化状态。因此，c-di-GMP浓度的个体细胞异质性受细胞分裂后趋化细胞器的活性和不对称遗传的调节。C-di-GMP的异质性导致了运动行为的多样性。通过不对称分配产生不同浓度的c-di-GMP对环境中细菌种群的成功和生存可能是重要的，因为它允许各种运动行为。DOI：http://dx.doi.org/10.7554/eLife.01402.001细菌群体传统上被认为是由相同的细胞组成的。然而，尽管一个群体中的细菌可能在基因上是相同的，但各个细胞的生长速度、新陈代谢和运动能力等都不同。这种表型异质性在许多不同种类的细菌中都观察到了，在某些情况下，它可以归因于被称为第二信使的分子浓度的变化，这种分子有助于将信号从外部环境传递到细胞内的靶标。监测细胞内特定分子浓度的变化可能是具有挑战性的，但研究人员最近开发了一种基于FRET(福斯特共振能量转移的缩写)的显微镜形式，可以测量单个细胞内名为环二鸟酸酯(c-di-GMP)的第二种信使分子的水平。这项技术被用于研究铜绿假单胞菌，这是一种细菌，它有一个开瓶器形状的螺旋桨，使它能够在液体中游泳。铜绿假单胞菌分裂形成两个子细胞--一个有螺旋桨，一个没有螺旋桨。尽管没有螺旋桨的子细胞很快就会长出螺旋桨，但基于FRET的显微镜显示，有螺旋桨的子细胞比没有螺旋桨的子细胞含有更少的c-di-GMP，但这种差异背后的原因及其对细菌行为的影响尚不清楚。现在，Kulasekara等人。结果表明，继承螺旋桨的细胞含有一种降解c-di-GMP的酶，第二信使分子的低水平--由酶集中在螺旋桨底部附近引起，以及使细菌能够游向营养来源的蛋白质(CHEA)的存在--导致游泳速度更快，对营养的反应增强。换句话说，尽管这两个子细胞在基因上是相同的，但由于第二信使分子的水平不同，它们的行为非常不同。细菌种群中异质性的存在可能会导致在不断变化的不同环境中提高成功率和存活率，这项工作为类似的研究奠定了基础，即是什么在其他细菌种群中建立了异质性。DOI：http://dx.doi.org/10.7554/eLife.01402.002
Individual cell heterogeneity is commonly observed within populations, although its molecular basis is largely unknown. Previously, using FRET-based microscopy, we observed heterogeneity in cellular c-di-GMP levels. In this study, we show that c-di-GMP heterogeneity in Pseudomonas aeruginosa is promoted by a specific phosphodiesterase partitioned after cell division. We found that subcellular localization and reduction of c-di-GMP levels by this phosphodiesterase is dependent on the histidine kinase component of the chemotaxis machinery, CheA, and its phosphorylation state. Therefore, individual cell heterogeneity in c-di-GMP concentrations is regulated by the activity and the asymmetrical inheritance of the chemotaxis organelle after cell division. c-di-GMP heterogeneity results in a diversity of motility behaviors. The generation of diverse intracellular concentrations of c-di-GMP by asymmetric partitioning is likely important to the success and survival of bacterial populations within the environment by allowing a variety of motility behaviors. DOI: http://dx.doi.org/10.7554/eLife.01402.001 Bacterial populations have traditionally been assumed to be made up of identical cells. However, while the bacteria within a population may be genetically identical, individual cells have different growth rates, metabolisms and motilities, among other things. This ‘phenotypic heterogeneity’ has been observed in many different species of bacteria, and in some cases it can be attributed to changes in the concentration of molecules called second messengers that help to relay signals from the external environment to targets within the cell. It can be challenging to monitor changes in the concentration of specific molecules inside cells, but researchers recently developed a form of microscopy based on FRET (short for Forster resonance energy transfer) that can measure the levels of a second messenger molecule called cyclic di-guanylate (c-di-GMP) inside individual cells. This technique was used to study P. aeruginosa, a bacterium that has a single corkscrew-shaped propeller that enables it to swim through liquid. P. aeruginosa divides to form two daughter cells—one with a propeller and one without. Although the daughter cell that does not have a propeller quickly grows one, FRET-based microscopy revealed that the daughter cell with a propeller had less c-di-GMP than the daughter without a propeller, but the reasons underlying this difference and its effects on bacterial behavior were not clear. Now Kulasekara et al. show that the cell that inherits the propeller contains an enzyme that degrades c-di-GMP, and that the low levels of this second messenger molecule—caused by the enzyme being concentrated near the base of the propeller, and the presence of a protein (CheA) that enables the bacteria to swim towards sources of nutrients—result in faster swimming speeds and increased responsiveness to nutrients. In other words, although the two daughter cells are genetically identical, they behave quite differently because of the different levels of this second messenger molecule. The existence of heterogeneity within a bacterial population likely leads to increased success and survival within changing diverse environments, and this work sets the stage for similar investigations into what establishes heterogeneity in other bacterial populations. DOI: http://dx.doi.org/10.7554/eLife.01402.002