Cyclic Diguanylate, A Novel Secondary Messenger in Bacteria

通过微生物基因组学已经揭示了许多未知功能的保守蛋白质结构域，这表明微生物生理学，代谢和行为的重要领域仍然未被探索。本研究旨在研究广泛分布于不同细菌中的包含GGDEF和EAL结构域的蛋白质的功能。GGDEF和EAL结构域参与不寻常的核苷酸环二鸟苷酸（c-di-GMP）的合成和水解。该项目的主要假设是，c-di-GMP是细菌中重要的未被重视的第二信使。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，使用代谢多功能的变形杆菌，Rhodobacter sphaeroides作为模型。初步数据表明，R.类球蛋白含有参与c-di-GMP的合成（二鸟苷酸环化酶）和水解（磷酸二酯酶）的酶。该项目的初始重点将放在两个R。sphaeroides c-di-GMP-特异性磷酸二酯酶，命名为BphG和BphH，其含有光敏色素型结构域并且可能代表独特结构的光感受器。在R. sphaeroides导致R.类球孢菌转录组揭示c-di-GMP影响基因表达的机制是该项目的另一个目的。结合分子遗传学，转录组学和生物化学的方法将被用来解决这些问题。这项研究将填补一个明显的空白，在我们的细菌细胞的理解所造成的一个潜在的重要的第二信使，c-di-GMP的疏忽。c-di-GMP作用的阐明预计对各种细菌（包括农业、环境和医学上重要的物种）中的信号转导领域具有显著影响。该项目将为高中生、本科生、研究生和博士后学生的跨学科培训提供充足的机会。

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.