Cyclic Diguanylate, A Novel Secondary Messenger in Bacteria

微生物基因组学揭示了许多功能未知的保守蛋白结构域，这表明微生物生理学、代谢和行为的重要领域仍未被探索。本研究旨在研究广泛分布于不同细菌中的含有GGDEF和EAL结构域的蛋白的功能。GGDEF和EAL结构域参与了不寻常核苷酸环二胍酸c-二gmp的合成和水解。本项目的主要假设是c-di-GMP是细菌中重要的未被充分认识的第二信使。该项目的长期目标是阐明c-di-GMP的作用，并揭示其运作机制，使用代谢多样的变形菌，球形红杆菌作为模型。初步研究表明，圆木含有合成二胍酸环化酶和水解c-二gmp的酶（磷酸二酯酶）。这个项目最初的重点将放在两个R. sphaeroides c-di- gmp特异性磷酸二酯酶上，命名为BphG和BphH，它们含有光敏色素型结构域，可能代表独特结构的光感受器。球形田鼠细胞内c-二- gmp池的耗竭导致球形田鼠转录组发生特异性变化。揭示c-二gmp影响基因表达的机制是本项目的另一个目的。分子遗传学、转录组学和生化方法的结合将被用来解决这些问题。这项研究将填补我们对细菌细胞的理解上的明显空白，这是由于对潜在重要的第二信使c-di-GMP的疏忽造成的。阐明c-二gmp的作用预计将对各种细菌的信号转导领域产生重大影响，包括农业、环境和医学上重要的物种。该项目将为高中生、本科生、研究生和博士后的跨学科培养提供充足的机会。

The numerous conserved protein domains of unknown function have been revealed through microbial genomics, which suggests that significant areas of microbial physiology, metabolism and behavior remain unexplored. This research is aimed at investigating functions of proteins containing GGDEF and EAL domains that are broadly distributed in diverse bacteria. The GGDEF and EAL domains are involved in synthesis and hydrolysis of the unusual nucleotide, cyclic diguanylate, c-di-GMP. The main hypothesis of this project is that c-di-GMP is an important underappreciated second messenger in bacteria. The long-term goals of the project are to elucidate the role of c-di-GMP and to reveal the mechanisms by which it operates using the metabolically versatile proteobacterium, Rhodobacter sphaeroides, as a model. Preliminary data indicate that R. sphaeroides contains enzymes involved in both synthesis (diguanylate cyclases) and hydrolysis (phosphodiesterases) of c-di-GMP. Initial emphasis of this project will be placed on two R. sphaeroides c-di-GMP-specific phosphodiesterases, designated BphG and BphH, which contain phytochrome-type domains and are likely to represent photoreceptors of unique structure. The depletion of the intracellular pool of c-di-GMP in R. sphaeroides results in specific changes in the R. sphaeroides transcriptome. Uncovering mechanisms by which c-di-GMP affects gene expression is another aim of this project. A combination of molecular genetic, transcriptomics and biochemical approaches will be employed to address these questions.This research will fill an apparent void in our understanding of the bacterial cell resulting from an oversight of a potentially important second messenger, c-di-GMP. Elucidation of the role of c-di-GMP is anticipated to have a significant effect on the field of signal transduction in various bacteria, including agriculturally, environmentally and medically important species. This project will provide ample opportunities for interdisciplinary training of high school, undergraduate, graduate and postdoctoral students.