Collaborative Research: Ecology of microbial mats at seamount associated Fe-rich hydrothermal vent systems

微生物生态学中的一个重大挑战是了解是什么驱动了微生物群落的结构。最近发现的一类新的变形杆菌，即泽塔变形杆菌，与海洋深处海底火山富含铁的热液喷口的微生物垫有关。这些细菌只能以铁为能源生长，并固定二氧化碳。在富含铁的微生物垫子中，ZetaProtecteria是优势细菌种群；然而，它们在大多数其他深海或海洋生境中很少见，这表明它们可能仅限于以氧气和铁的梯度为特征的特定生态位。最近的发现扩大了它们的范围，包括从深海地壳钻孔收集的流体，沿海盐沼中的铁矿床，以及与钢铁相关的生物腐蚀，表明海洋泽塔变形杆菌是世界性的。这些海洋铁氧化细菌的一个独特特性是，它们以丝状鞘或茎状结构的形式产生形态上不同的氧化铁结构。这些结构很容易被光学显微镜识别，电子显微镜开始显示它们之间的细微差异，这可能是对不同种群的铁氧化细菌的诊断。铁氧化细菌的另一个不同寻常的方面是，它们产生大量的氧化物，而细菌的生物量相对较少。因此，氧化物形成一种基质，影响它们生长的微生物垫中的水和营养物质流动，进而可能影响生活在垫上的其他细菌和古生菌的生长。在生态方面，PI认为这使他们成为形成MAT主要结构矩阵的关键物种，并设计了有利于MAT生态系统内特定细菌种群生长的环境。PIS建议使用高分辨率MAT采样技术来调查MAT生态系统的结构，并将其与现代分子方法(即单细胞元基因组学)和喷口流体的地球化学测量相结合，以将形态和功能多样性与系统发育和生理多样性结合起来。由于齐塔蛋白细菌是古老的，具有独特的新陈代谢和形态属性，并且似乎局限于定义明确的栖息地，它们为理解推动微生物多样性和进化的基本生态概念提供了一个有趣的模型。更广泛的影响：对于对地球科学和海洋学领域感兴趣的科学家来说，更好地了解包括ZetaProducteria在内的铁氧化细菌是非常重要的，因为它们说明了微生物如何从根本上影响地球化学循环和矿物沉积。此外，在数亿年(甚至数十亿年前)的地质记录中，仍可以识别出与齐塔变蛋白细菌产生的形态结构相似的形态结构，使它们具有古生物学意义，并可能具有外部生物学意义。随着对现存人口的了解不断增加，它们也有可能帮助我们了解过去地球历史上的环境变化。这项工作将提供丰富的教育和外展机会，包括研究生和博士后教育、本科生研究经验和教师培训。此外，参与的科学家还参与了一些项目，让公众了解科学研究是如何进行的，以及基本性质的发现如何最终造福人类。

A grand challenge in microbial ecology is to understand what drives the structure of microbial communities. A recently discovered novel class of Proteobacteria, the Zetaproteobacteria, are associated with microbial mats at iron rich hydrothermal vents at submarine volcanoes deep in the ocean. These bacteria only grow using iron as an energy source and fix carbon dioxide. Within iron rich microbial mats, Zetaproteobacteria are the dominant bacterial population; however they are rare in most other deep-sea or marine habitats, suggesting they may be restricted to specific niches characterized by gradients of oxygen and iron. Recent discoveries have expanded their range to fluids collected from deep ocean crust boreholes, iron deposits in coastal saltmarshes, and with steel associated bio-corrosion, demonstrating that marine Zetaproteobacteria are cosmopolitan. A unique property of these marine iron oxidizing bacteria is that they produce morphologically distinct iron oxide structures in the form of filamentous sheaths or stalk-like structures. These structures are easily recognized by light microscopy, and electron microscopy is beginning to reveal subtle differences among them that may be diagnostic of different populations of iron oxidizing bacteria. Another unusual aspect of iron oxidizing bacteria is that they produce large quantities of oxides with relatively little bacterial biomass. As a result, the oxides form a matrix that influences water and nutrient flow in the microbial mats where they grow, and in turn, may influence the growth of other groups of bacteria and archaea that live in the mats. In an ecological context, the PIs believe this makes them a keystone species that form the predominant structural matrix of the mat, and engineer an environment conducive for growth of specific bacterial populations within the mat ecosystem. The PIs propose to use high resolution mat sampling techniques to investigate the architecture of mat ecosystems and couple these with modern molecular methods (i.e., single-cell metagenomics) and geochemical measurements of the vent fluid to couple morphological and functional diversity to phylogenetic and physiological diversity. Because the Zetaproteobacteria are ancient, have unique metabolic and morphological attributes, and appear to be restricted to a well-defined habitat, they offer an interesting model for understanding fundamental ecological concepts that drive microbial diversity and evolution. Broader Impacts: A better understanding of iron oxidizing bacteria that include Zetaproteobacteria is of fundamental interest to scientists interested in areas of earth science and oceanography because they illustrate how microbes can fundamentally influence geochemical cycling and mineral deposition. Furthermore, morphological structures similar to those produced by Zetaproteobacteria can still be identified hundreds of millions (and possibly billions) of years back in the geological record, making them of paleontological, and potentially of exobiological, interest. As knowledge of extant populations grow, it is possible they will also help to inform us of environmental change in past Earth history. A wealth of educational and outreach opportunities will be made possible by this work, including graduate and postdoctoral education, research experiences for undergraduates, and teacher training. In addition the participating scientists are involved in a number of programs to make the general public aware of the process of how scientific research is conducted, and how discoveries of a fundamental nature can ultimately benefit humankind.