Carbon Fixation Pathways in Marine Chemoautotrophic, Mesophilic Crenarchaeota: Implications for the Oceanic Carbon Cycle

智力上的优点。海洋的中层和深层区域是地球上最大的连续生境，但我们对生活在这一区域的微生物种类及其活动的全球影响知之甚少。传统上，这一区域中微生物的作用被视为有机物的降解者，同时释放二氧化碳。然而，最近这一观点受到质疑，因为发现属于海洋crenarchaeota group 1（MG 1）的海洋Crenarchaeota实际上可能是自养生物，而海洋crenarchaeota在中层和深海区的原核细胞数量中占主导地位。然而，到目前为止，几乎没有人知道这一广泛的，可能是不同的生物群的代谢能力。该项目旨在解决以下问题：自养嗜温泉古菌如何固定CO2？是否存在嗜温、化能自养的泉古菌，它们通过硫化物或氢氧化获得能量？如果是，在不同的代谢群中是否存在不同的自养固碳途径？嗜温和嗜热Crenarchaeota之间在CO2固定方面存在什么差异？这些差异能告诉我们什么关于古龙的进化？我们对全球海洋碳固定和海洋碳循环的看法有什么后果？为了解决这些问题，研究人员建议首先阐明铵氧化古菌所使用的碳固定途径，我们目前在培养中并且已经从各种环境中获得。其次，他们建议在已经由国家科学基金会资助的东太平洋海隆北纬9度热液喷口研究巡航期间，从营养线、最低含氧区、热液羽流和热液喷口附近获得分离物。目前的工作假设是，这些Crenarchaeota内的自养固碳不是通过卡尔文循环进行的，而是通过另一种CO2固定途径。如果这是真的，这将意味着海洋中大量的碳固定不是通过卡尔文循环进行的，这将导致我们重新考虑目前对海洋二氧化碳固定和海洋碳循环的看法。这项工作特别侧重于培养，分离和进一步表征这些生物体，从而理想地补充了其他实验室利用环境基因组技术正在进行的研究。更广泛的影响。这项工作解决了全球碳循环的一个重要但知之甚少的方面，这是一个具有重大社会意义的主题。这项工作的结果对于完善当前的碳循环模型至关重要，并可能从根本上改变目前对碳在海洋中如何转移的看法。该项目有各种教育组成部分，从当地学校的教学、本科生的参与到博士后支持。预计结果将成为媒体采访（印刷和广播）的主题，并被整合到PI实验室或机构现有的课程和网页中。

Intellectual merit. The meso- and bathypelagic realm of the oceans represents the largest continuous habitats on Earth, yet we know very little about the kind of microbes living in this zone and the global impact of their activities. Traditionally, the role of microbes in this zone has been seen as degraders of organic matter with a concomitant release of CO2. However, recently this perception has been called into question by the finding that planktonic Crenarchaeota belonging to the marine crenarchaeota group 1 (MG1), which dominate the prokaryotic cell numbers in the meso-and bathypelagic zone, could actually be autotrophs. However until now, almost nothing is known about the metabolic capacities of this extensive and probably diverse group of organisms. This project is designed to address the following questions:. How do autotrophic, mesophilic Crenarchaeota fix CO2?. Do mesophilic, chemolithoautotrophic Crenarchaeota exist that obtain energy through sulfide or hydrogen oxidation?. If yes, are there different autotrophic carbon fixation pathways in different metabolic groups?. What differences exist regarding CO2 fixation between mesophilic and thermophilic Crenarchaeota?. What can these differences tell us about the evolution of Archaea?. What are the consequences for our view of global oceanic carbon fixation and the oceanic carbon cycle in general?To address these questions, the investigators propose first to elucidate the carbon fixation pathway used by ammonium-oxidizing archaea that we have currently in culture and that have been obtained from a variety of environments. Secondly, they propose to obtain isolates from the nutricline, the oxygen minimum zone, hydrothermal plumes, and the general vicinity of hydrothermal vents during an already NSF-funded research cruise to the hydrothermal vents at 9N on the East Pacific Rise. The current working hypothesis is that autotrophic carbon fixation within these Crenarchaeota is not carried out via the Calvin cycle, but rather via an alternative CO2 fixation pathway. If true, this would mean that a significant amount of carbon fixation in the ocean is not carried out via the Calvin cycle, leading to a reconsideration of our current view of oceanic CO2 fixation and the oceanic carbon cycle in general. This work specifically focuses on cultivating, isolating and further characterizing these organisms and thus ideally complements ongoing research in other laboratories utilizing environmental genomic techniques. Broader impacts. This work addresses an important, yet poorly understood aspect of the global carbon cycle, a topic that has a significant societal relevance. Results of this work will be essential to refine current carbon cycle models, and potentially fundamentally alter the current view of how carbon is transferred in the ocean. This project has a variety of educational components ranging from teaching at local schools and the involvement of undergraduates to post-doctoral support. It is expected that results will be the topic of media interviews (print and radio) as well as be integrated into coursework and web-pages existing either in the PI's labs or at the institution.