SGER: Developing Metal-Tagged DNA Probes for High Resolution Imaging of Microbial Phylotype Distributions and Nanoscale Mineral/Microbe Associations in Environmental Samples

高分辨率电子显微镜(EM)图像放大了微生物及其微生境，揭示了微生物细胞及其物质环境的细微特征。EM图像在研究微生物如何与天然和人造材料相互作用方面可能有很大的用处。然而，自然样品中共存的多种类型的微生物通常不能仅凭外观来区分。此外，当“缩小”时，不可能看到安装在EM上的样品中微生物的整体分布。必须发明一种在EM图像中直观区分特定微生物遗传类型的方法，以充分开发电子显微镜的潜力，以了解环境中原位微生物的分布和活动。已经向教授颁发了一笔补助金。加州大学圣巴巴拉分校的雷切尔·M·海蒙和帕特里夏·霍尔登，以及伍兹霍尔海洋研究所的斯特凡·西弗特博士，为开发将贴在选定微生物的DNA序列上的金属“标签”而工作。当金属被用来产生电磁图像的电子束激发时，金属将发出X射线，并允许在高倍和低倍下对目标生物进行明确的视觉识别。这种方法将解决用电子束成像的微生物的空间分布和身份识别方面存在的问题，并将使人们有可能在小范围内了解与微生物生命相关的微生物和矿物的组合。所提出的金属标记DNA探针在了解微生物与环境相互作用方面的应用非常广泛。该方法有望成为研究自然环境中微生物活动的功能、生态和环境影响的标准工具。例如，Haymon、Holden和Sievert博士希望将这项新技术应用于土壤中微生物的研究，在土壤中微生物对有毒人为化合物的生物降解非常重要，以及在热液系统中微生物在极端高温和化学条件下与地质材料相互作用。

ABSTRACTHigh-resolution electron microscope (EM) images greatly magnify microbes and their microhabitats, and reveal minute features of microbial cells and their material surroundings. EM images potentially are of great use in studying how microbes interact with natural and man-made materials. However, the many types of microorganisms co-existing in natural samples typically cannot be distinguished from one another based on appearance alone. Furthermore, when "zoomed out" it is not possible to see the overall distribution of microbes in EM-mounted samples. A means of visually distinguishing specific genetic types of microbes in EM images must be invented to fully exploit the potential of electron microscopy for learning about in situ microbial distribution and activity in the environment. A grant has been awarded to Profs. Rachel M. Haymon and Patricia Holden at University of California, Santa Barbara, and to Dr. Stefan Sievert at Woods Hole Oceanographic Institution, for development of metallic "tags" that will attach to DNA sequences of selected microbes. When the metals are excited by electron beams used to generate EM images, the metals will emit X-rays and permit unambiguous visual identification of the targeted organisms at both high and low magnifications. This method will solve the existing problems in distinguishing spatial distributions and identities of microbes imaged with electron beams, and will make it possible to understand associations of microbes and minerals at small scales that are relevant to microbial life.Applications of the proposed metal-tagged DNA probes to understanding how microbes interact with the environment are vast. It is expected that the proposed method will become a standard tool for studying the function, ecology, and environmental impact of microbial activities in natural environments. For example, Drs. Haymon, Holden, and Sievert hope to apply this new technique to studies of microbes in soils, where microbes are important to biodegradation of toxic anthropogenic compounds, and in hydrothermal systems, where microbes interact with geologic materials under extreme thermal and chemical conditions.