Dimethylsulfoniopropionate Metabolism by Marine Bacteria

知识优势：二甲基磺丙酸盐（DMSP）占海洋表层浮游植物固定碳的10%，是强效抗温室气体二甲基硫化物（DMS）的前体，二甲基硫化物是大气中最大的天然硫源。海洋微生物群落中DMSP代谢有两种相互竞争的途径。大多数DMSP通过“去甲基化”途径被海洋细菌加工，从而形成甲硫醇（MeSH）和其他含硫化合物。一小部分通过“裂解”途径代谢成DMS，导致硫排放到大气中。DMSP被引导到这些途径之一的点，被称为“细菌开关”，代表了全球硫循环的关键控制点之一。基于最近发现的这些途径所需的基因，本研究将研究模式海洋细菌的细菌开关的生理和生化基础。研究人员将检查这些途径中的酶，以进一步了解它们在细胞中的作用。DMSP代谢的其他环境和生理控制将在整个细胞中进行表征。将具体测试四种作用：DMSP作为碳和硫源，作为相容溶质，以及作为抗氧化剂。此外，许多去甲基化途径的基因广泛存在于DMSP不丰富的陆地和其他栖息地，并被假设在蛋氨酸代谢中起作用。这一潜在作用也将受到考验。综上所述，细菌DMSP代谢在全球硫循环中起着重要作用。这项研究旨在了解细菌代谢DMSP的原因。更广泛的影响：该项目的更广泛的影响包括在佐治亚大学微生物和海洋科学系培养两名博士生和一名博士后研究助理，并每年为一名本科生提供研究机会和指导。学生将获得微生物生理学、微生物生态学、酶学和环境科学的跨学科培训。在当地小学和高中的推广活动将强调原核生物的多样性、分解和碳循环、光合细菌以及细菌在形成地球大气层中的作用。它将为学生提供与分子微生物生态学的现代技术的动手工作的机会。通过提高我们对微生物控制DMS向大气演化的认识，本研究将有助于了解这些过程如何响应预测的气候变化以及减缓全球气候变化的潜在机会。

Intellectual Merit: Dimethylsulfoniopropionate (DMSP) accounts for up to 10% of the carbon fixed by marine phytoplankton in surface waters of the ocean and is the precursor to the potent anti-greenhouse gas dimethylsulfide (DMS), the largest natural source of sulfur to the atmosphere. Two competing pathways for DMSP metabolism operate in marine microbial communities. Most of the DMSP is processed by marine bacteria through the "demethylation" pathway, which leads to formation of methanethiol (MeSH) and other sulfur compounds. A smaller portion is metabolized via the "cleavage" pathway to DMS, resulting in sulfur emissions to the atmosphere. The point at which DMSP is directed to one of these pathways, referred to as "the bacterial switch", represents one of the critical regulatory points in the global sulfur cycle. Based upon recent discoveries of the genes necessary for these pathways, this research will examine the physiological and biochemical basis the bacterial switch in the model marine bacterium, Ruegeria pomeroyi. Research will examine the enzymes of the pathways to further understand how they function in cells. Other environmental and physiological controls of DMSP metabolism will be characterized in whole cells. Four roles will be specifically tested: DMSP as a carbon and sulfur source, as a compatible solute, and as an antioxidant. In addition, many of the genes of the demethylation pathway are widespread in terrestrial and other habitats where DMSP is not abundant and have been hypothesized to function in methionine metabolism. This potential role will also be tested. In conclusion, bacterial DMSP metabolism plays a fundamental role in the global sulfur cycle. This research seeks to understand why the bacteria metabolize DMSP. Broader Impacts: The broader impacts of the project include the training of two doctoral students and one postdoctoral research associate in the departments of Microbiology and Marine Sciences at the University of Georgia and providing research opportunities and mentoring for one undergraduate student per year. Students will obtain interdisciplinary training in microbial physiology, microbial ecology, enzymology and environmental sciences. Outreach activities at local elementary and high schools will emphasize prokaryotic diversity, decomposition and the carbon cycle, photosynthetic bacteria, and the role of bacteria in forming the earth's atmosphere. It will provide students opportunities for hands on work with modern techniques of molecular microbial ecology. By improving our knowledge of the microbial control of the evolution of DMS to the atmosphere, this research will provide understanding how these processes will respond to the predicted climate changes as well as potential opportunities for mitigation of global climate change.