Membrane vesicles produced by marine bacteria: origins, distributions, and functions

概述：一些细菌以微小的(直径200 nm)球形结构称为膜泡的形式释放少量的细胞膜。虽然这些小泡的功能已经在病原体中得到了探索，但对它们在海洋生态系统中的丰度和作用却一无所知。研究人员最近证明，世界海洋中数量占主导地位的光合作用细胞原氯球菌在生长过程中不断释放膜泡，他们还表明，这些结构确实在海洋样本中大量存在。细菌产生的膜小泡代表着海洋生态系统的一个主要新特征，可以提供关于微生物与其环境之间相互作用网络的重要线索。原氯球菌囊泡含有不同的大分子，包括脂类、蛋白质和核酸，这表明这些结构在海洋微生物群落中可能扮演着许多不同的角色。研究人员将使用原氯球菌模型系统和对几个野外地点的天然海水样本进行分析，以解决有关海洋中膜泡的生产和功能的基本问题。激励这项研究的主要问题包括：什么环境因素影响原氯球菌释放膜泡的速度，这能告诉我们什么关于这个过程的调节？海洋不同区域的囊泡丰度是如何变化的？在天然海水样本的小泡中发现了什么DNA？囊泡“元基因组”与细菌元基因组相比如何？这能告诉我们什么关于释放囊泡的生物的多样性？囊泡在海洋微生物生态系统中可能扮演什么样的生态角色？它们能促进水平的基因转移吗？它们能充当减少噬菌体捕食的“诱饵”吗？智力价值：膜小泡代表着海洋生态系统的一个主要新特征。这些离散的、有组织的结构可能会影响一些生物地球化学过程，包括水平基因转移；在细胞之间移动小分子、蛋白质或其他大分子；或作为其他细菌的固定碳来源。然而，我们对它们一无所知。这个项目将打开这个黑匣子，并帮助我们开始了解海洋中膜泡的丰度和来源，确定影响其产生的因素，并探索它们在海洋系统中的生态作用。通过这项研究，研究人员将开始建立海洋微生物生态学的一个新的研究领域，该领域有可能改变目前关于微生物与其生物和非生物环境相互作用的机制的范式。广泛的影响：研究人员将利用麻省理工学院提供的几种途径与代表性不足的群体合作。其中包括：麻省理工学院暑期研究计划Converge(周末预览)；SEED(周六教育计划)；Keys(女孩计划)，以及MIT Edgerton中心，为当地K-12班的访问提供便利。这位研究人员致力于向广大受众传播科学。国际和平协会已经出版了两本关于光合作用的儿童书籍(《活着的阳光》、《海洋阳光》、《学者》2009,2012；这两本书都获得了美国科学促进会颁发的“最佳儿童图画书”奖)，目前正在编写第三本，关于化石燃料和气候，将于2014年出版。该项目将在所涉博士后(S)的专业发展中发挥核心作用，拟议活动产生的数据将公布在公共网站上，包括原氯球菌门户网站(http://proportal.mit.edu/)，)和百科全书数据库(http://www.microvesicles.org)

Overview: Some bacteria are known to release small amounts of their cell envelope in the form of tiny ( 200 nm diameter) spherical structures known as membrane vesicles. While the functions of these vesicles have been explored in pathogens, nothing is known about their abundance or roles in marine ecosystems. The investigators have recently demonstrated that Prochlorococcus, the numerically dominant photosynthetic cell in the world's oceans releases membrane vesicles continually during growth, and they have shown that these structures are indeed found in abundance in ocean samples. Bacterially produced membrane vesicles represent a major new feature of ocean ecosystems and could provide important clues about the network of interactions among microbes and their environment. Prochlorococcus vesicles contain diverse macromolecules, including lipids, proteins, and nucleic acids, suggesting that these structures could play many varied roles within marine microbial communities. The researchers will use the Prochlorococcus model system and the analysis of natural seawater samples from several field sites to address fundamental questions about the production and function of membrane vesicles in the oceans. The overarching questions motivating this study include: What environmental factors influence the rate of release of membrane vesicles by Prochlorococcus, and what can this tell us about the regulation of this process? How does vesicle abundance vary in different regions of the oceans? What DNA is found in vesicles from natural seawater samples? How does the vesicle "metagenome" compare to the bacterial metagenome, and what can this tell us about the diversity of organisms that release vesicles? What ecological roles might vesicles play in marine microbial ecosystems? Can they facilitate horizontal gene transfer? Can they act as a "decoy" to reduce phage predation?Intellectual Merit: Membrane vesicles represent a major new feature in ocean ecosystems. These discrete, organized structures may influence a number of biogeochemical processes, including horizontal gene transfer; moving small molecules, proteins or other macromolecules between cells; or serving as a source of fixed carbon for other bacteria. Yet we know nothing about them. This project will open this black box, and help us begin to understand the abundance and sources of membrane vesicles in the oceans, determine factors affecting their production by the numerically dominant photoautotroph Prochlorococcus, and explore aspects of their ecological roles in marine systems. With this research, the investigators will begin to establish a new area of study in marine microbial ecology that has the potential to alter current paradigms about the mechanisms through which microbes interact with both their biotic and abiotic environment.Broader Impacts: The investigators will take advantage of several avenues available at MIT to work with under-represented groups. These include: the MIT Summer Research Program, CONVERGE (a preview weekend); SEED (a Saturday education program); KEYs (a program for girls), and the MIT Edgerton Center which facilitates visits from local K-12 classes. The investigator is committed to communicating science to broad audiences. The PI has published two children's books on photosynthesis (Living Sunlight, Ocean Sunlight, Scholastic 2009, 2012; both received "best children's picture book" awards from AAAS), and is currently working on a third, on fossil fuels and climate, which will appear in 2014. This project will play a central role in the professional development of the post-doc(s) involved and data resulting from the proposed activity will be posted on public web sites, including the Prochlorococcus Portal (http://proportal.mit.edu/), and the Vesiclepedia database (http://www.microvesicles.org)