Bacterial Cell-Wall Evolution

肽聚糖或细胞壁赋予细菌一个刚性结构，保护它不因渗透压而破裂，并有助于细胞形状。细菌细胞的形状是高度动态的，细胞可以根据环境从棒状到螺旋状再到圆形的形态变化。这些细胞形状的变化可能是在发育时间尺度上发生的转变，在单个细胞周期中发生，也可能通过细菌进化过程成为永久性的，以应对新的环境约束。例如，我最近描述了鼻咽细菌（这里是脑膜炎奈瑟菌和卡他莫拉菌）的过去演变。这两个物种在适应这个生态系统的过程中都经历了类似的从杆状到球菌状的细胞形状转变。因此，可以观察到它们细胞壁结构的变化。通过采用进化方法来检测特定的遗传事件，有可能揭示一些可能参与这些表型改变的蛋白质的功能。在这项研究的背景下，我们能够阐明在所有球菌中缺失的YacF （ZapD）作为细菌细胞延伸和分裂的协调者的未被揭示的作用。但其确切的分子机制尚不清楚。***研究项目的长期目标是通过发现新的参与者来更好地理解细胞壁的调节，并描述这些调节现象在细菌细胞周期中的重要性。在这个提议中，我们的目的是深入描述背后的分子机制YacF协调细胞周期在杆菌。我们将检验YacF在细胞伸长过程中及时抑制细胞分裂的假设。此外，我们将建立一个生物信息学工具，将允许检测细微的修饰，如在细菌进化过程中发生的氨基酸变化。在这种情况下，我们想描述伴随球虫转变的突变，这种突变可能改变了蛋白质功能、蛋白质-蛋白质相互作用或基因调控。最后，使用类似的进化类型方法，我们在奈瑟菌科或莫拉菌科中使用，我们将通过寻找自然形态畸变（这里是Simonsiella muelleri）来揭示涉及细胞壁调节的其他参与者。***我们拥有从生物信息学、基因组学、分子生物学到微生物生态学的多学科专业知识，旨在了解细菌细胞壁进化背后的机制和这种变化的原因。对这些机制的更好理解将最终允许改进工业上重要的细菌菌株或开发新的方法来控制细菌数量，这些方法可能适用于许多领域，如农业、生物技术和医学。********* **

The peptidoglycan or cell wall gives the bacteria a rigid structure, protects it from bursting due to osmotic pressure and contributes to cell shape. Bacterial cell shape is highly dynamic and cells are able to change from rod to spiral to round morphologies depending on their environment. These cell shape changes can be a transition that can happen on the developmental time scale, during a single cell cycle or it can become permanent through the course of bacterial evolution to respond to new environmental constraints. For example, I recently described the past evolution of nasopharyngeal bacteria (herein Neisseria meningitidis and Moraxella catarrhalis). Both species have undergone a similar cell-shape transition from rod to coccus during their adaptation to this ecosystem. As a consequence, changes in the structure of their cell-wall could be observed. By taking an evolutionary approach to detect specific genetics events, it is possible to expose the function of some proteins that could be involved in these phenotypic alterations. In the context of this study, we were able to shed light on an unrevealed role of YacF (ZapD), deleted in all cocci, as a coordinator of bacterial cell elongation and division. But the precise molecular mechanism is still unknown. ***The long-term goal of the research program is to better understand the regulation of the cell-wall by discovering new players and describe the importance of these regulation phenomena in the bacterial cell cycle. In this proposal, we aim at describing in depth the molecular mechanisms behind YacF coordination of the cell cycle in bacilli. We will test the hypothesis that YacF is timely inhibiting cell division during the course of cellular elongation. In addition, we will build a bioinformatics tool that will allow the detection of subtle modifications such as amino-acids change that happen during bacterial evolution. In this case, we want to describe mutations concomitant with the coccoid transition that could have changed protein function, protein-protein interaction or genes regulation. Finally, using similar evolutionary type of methods as we used in the Neisseriaceae or Moraxellaceae family, we will reveal other players implicated in the cell-wall regulation by searching for natural morphological aberration (herein Simonsiella muelleri). ***Equipped with multi-disciplinary expertise from bioinformatics, genomics and molecular biology to microbial ecology, we aim at understanding the mechanisms behind bacterial cell-wall evolution and the reasons of such changes. A better understanding of these mechanisms will ultimately allow improvement of industrially important bacterial strains or the development of new approaches towards bacterial population control that could be applicable to numerous fields such as agriculture, biotechnology and medicine.********* **