Cyclic Dimeric GMP, a Novel Second Messenger in Bacteria: Molecular Mechanisms

环状二聚鸟苷单磷酸，c-di-GMP，是参与细菌从单一活动细胞到表面附着的多细胞群落(生物膜)生活方式转换的关键分子。C-di-GMP通过影响细菌的运动能力、表面黏附、细胞外基质的合成、抗逆性和毒力来控制这种生活方式的转变。获得对c-di-GMP如何发挥作用的机制洞察在细菌学中是至关重要的。目前，参与c-di-GMP合成和水解的大量酶(大多数变形杆菌中有几十种)与已知的c-di-GMP受体或效应蛋白的少量(低个位数)之间存在着明显的差距。这一缺口表明许多c-di-GMP受体逃脱了识别。该项目的长期目标是识别新的c-di-GMP受体，并揭示它们在模式细菌大肠杆菌中发挥作用的分子机制。在这个项目中，新的c-di-GMP受体将通过遗传手段和基于亲和力的捕获来识别。由于c-di-GMP像其他第二信使一样，通过保守的分子机制发挥作用，因此来自大肠杆菌的见解有望为控制各种具有医学、农业、环境和生物技术意义的细菌物种的行为提供参考。这项提议的更广泛的优点在于理解了控制细菌行为的机制。这一理解对于设计药理干预措施至关重要，使我们能够以令人满意的方式操纵细菌。该项目将为研究生和本科生提供生物信息学、细菌遗传学、蛋白质配基生物化学和生理学方面的跨学科培训机会，这些学生将构成核心研究人员。它还将为参加暑期研究学徒计划的少数民族高中生提供研究经验。项目成果将在科学会议上提出，并在研究论文和面向更广泛受众的文章中发表。

Cyclic dimeric guanosine monophosphate, c-di-GMP, is a key molecule involved in the lifestyle switch in bacteria, from single motile cells to surface-attached multicellular communities (biofilms). c-di-GMP controls this lifestyle switch by affecting bacterial motility, adhesion to surfaces, synthesis of extracellular matrix, stress resistance, and virulence. Gaining mechanistic insights into how c-di-GMP functions is of fundamental importance in bacteriology. Currently, a glaring gap exists between the large numbers of enzymes involved in c-di-GMP synthesis and hydrolysis (several dozen in most proteobacteria) and the small numbers (low single digits) of known c-di-GMP receptors, or effector proteins. This gap indicates that many c-di-GMP receptors have escaped identification. The long-term objective of this project is to identify new c-di-GMP receptors and uncover molecular mechanisms through which they operate in a model bacterium, Escherichia coli. In this project, new c-di-GMP receptors will be identified by genetic means as well as by the affinity-based capture. Because c-di-GMP, like other second messengers, works though conserved molecular mechanisms, it is expected that the insights derived from E. coli will inform strategies on controlling behavior of various bacterial species of medical, agricultural, environmental and biotechnological significance. The broader merit of this proposal lies in understanding the mechanisms that control bacterial behavior. This understanding is critical for designing pharmacological interventions that would allow us to manipulate bacteria in desirable ways. This project will offer interdisciplinary training opportunities in bioinformatics, bacterial genetics, protein-ligand biochemistry, and physiology to graduate and undergraduate students who will comprise the core research personnel. It will also provide research experiences to minority high school students enrolled in the Summer Research Apprenticeship Program. The project results will be presented at scientific meetings and published in research papers as well as in the articles for broader audiences.