Collaborative Research: A Model for Divergent Bacterial Signaling Networks; Linking New Cyclic Dinucleotides to Environmental and Electrical Lifestyles

一些环境细菌具有检测、附着和与金属颗粒发生反应的能力。这一过程导致必需矿物质释放到河流和湖泊中，并降低了正在进行生物修复的废弃地中重金属污染物的毒性。这个合作项目的重点是最近发现的一种机制，使细菌能够感知这些重要的金属并做出反应。由于这些细菌也能够附着在电极上，因此监测金属去污染的新技术可以利用这些传感系统。研究人员将使用分子技术来观察细菌内部，在那里他们将确定这些金属的感应如何打开和关闭基因和蛋白质，以响应不同类型的金属表面。该项目将提供跨学科的大学水平的培训，包括明尼苏达州的体验式生物学模块，以及为加州的社区学院和本科生服务的实习计划。作为对K-12学生的推广，我们将采用实践教育演示，展示化学、水质和这种独特的微生物-电活动之间的联系。最后，我们将扩展YouSTEM.org，这是一个由哈蒙德实验室为普通公众创建的网站，用于查找有关免费K-12 STEM项目的信息，添加到明尼阿波利斯/圣保罗地区。环状双GMP(CdiG)是一种几乎普遍的细菌信号，它控制着从自由生活状态到表面附着生物膜的转变。然而，环境细菌有许多与表面相关的生活方式，不同于经典的生物膜状态。因此，一个巨大的挑战是解释信号网络如何只利用一个细胞内输出分子来控制不同的适应。最近发现了一种新的替代解决方案，基于调节不同遗传程序的多个环状二核苷酸。新发现的信号循环AMP-GMP(CAG)是硫还原地杆菌在细胞外金属氧化物颗粒上生长所必需的，这些颗粒通常存在于沉积物和含水层中。在同一生物体中，经典信号cdiG对于作为附着的导电生物膜将电子传递到产甲烷菌或电极表面的生长至关重要。值得注意的是，在地质杆菌中新发现的CAG信号通路使用了以前与cdiG信号相关的生物分子部分，揭示了仅cdiG信号网络的整体模型中的裂缝。合成CAG的GGDEF酶的亚类被称为DNCG，在不同的细菌门中都是保守的，包括变形杆菌、酸性细菌和脱铁细菌。然而，对DNCG活性的调节和对CAG反应的下游效应器在很大程度上是未知的。这一合作研究项目将为新发现的CAG信号通路建立一个全面的部分图谱和调控模型，建立一个分子工具箱来研究它如何在体内与经典的cdiG通路一起运作，并定义信号如何控制环境中重要的表型。

Some environmental bacteria have the ability to detect, attach to and react with metal particles. This process causes release of essential minerals into rivers and lakes, and reduces toxicity of heavy metal contaminants in waste sites undergoing bioremediation. This collaborative project focuses on the recent discovery of a mechanism that enables bacteria to sense and respond to these important metals. As these bacteria are also capable of attaching to electrodes, new techniques for monitoring metal decontamination could harness these sensing systems. The researchers will use molecular techniques to look inside the bacteria, where they will determine how sensing of these metals switches genes and proteins on and off in response to different types of metal surfaces. This project will provide cross-disciplinary college-level training including experiential biology modules in Minnesota and internship programs serving community college and undergraduate students in California. As outreach to K-12 students, we will adapt hands-on educational demonstrations that exhibit the link between chemistry, water quality, and this unique microbial-electrical activity. Finally, we will expand YouSTEM.org, a website created by the Hammond lab for the general public to find information about free K-12 STEM programs, to add the Minneapolis/St. Paul area.Cyclic di-GMP (cdiG) is a near-universal bacterial signal that controls the transition from a free-living state to a surface-attached biofilm. However, environmental bacteria have many surface-associated lifestyles distinct from the classic biofilm state. Thus, a grand challenge is to explain how signaling networks utilize only one intracellular output molecule to control diverse adaptations. A recently discovered novel alternative solution has been discovered, based on multiple cyclic dinucleotides that regulate distinct genetic programs. The newfound signal cyclic AMP-GMP (cAG) is required when Geobacter sulfurreducens grows on extracellular metal oxide particles commonly found in sediments and aquifers. In this same organism, the classical signal cdiG is essential for growth as an attached conductive biofilm to relay electrons to methanogens or electrode surfaces. Strikingly, the newfound cAG signaling pathway in Geobacter uses biomolecular parts previously associated with cdiG signaling, revealing cracks in the monolithic model of a cdiG-only signaling network. The sub-class of GGDEF enzymes that synthesize cAG, called DncG, are conserved throughout diverse Bacterial phyla, including Proteobacteria, Acidobacteria, and Deferribacteria. However, regulators of DncG activity and downstream effectors that respond to cAG are largely unknown. This collaborative research project will establish a comprehensive parts map and regulatory model for the newfound cAG signaling pathway, build a molecular toolkit to study how it operates alongside classical cdiG pathways in vivo, and define how the signal controls environmentally important phenotypes.