Collaborative Research: MIP: Physiology and Molecular Ecology of Thermophilic Nitrate-reducing Microorganisms at Deep-sea Hydrothermal Vents

这项研究将调查深海热液喷口嗜热硝酸盐还原微生物的生理和生态。由于微生物对深海热液喷口氮循环的贡献在很大程度上仍然未知，这项研究旨在填补这一空白。最近的研究表明，在海洋地热环境中出现了新的嗜热微生物，它们将硝酸盐的还原与自养CO2固定结合起来。深海喷口的这种微生物群落具有双重生态意义：1）这些生物通过固定CO2促进初级生产力，2）它们的硝酸盐呼吸代谢（即将NO3-还原为NO2-、N2或NH 4+）意味着氮保存在喷口系统内，并再循环进入喷口氮循环。这项研究将结合新的培养和分子技术与稳定同位素分析，以探索硝酸盐还原微生物的生理学，并评估其功能多样性和活性。通过建立生理、生殖和活动之间的联系，这项研究将有助于我们了解深海喷口硝酸盐还原生物的生态相关性，以及它们对碳和氮循环的贡献。这项研究还将有助于扩大与CO2固定和NO3还原相关的基因数据库，从而改进用于监测环境中这些微生物过程的检测工具。培训机会将提供给一名研究生和几名本科生，以及与几个NSF赞助的项目（例如，中大西洋海洋科学教育卓越中心和海上学生实验）也将得到支持。

This study will investigate the physiology and ecology of thermophilic, nitrate-reducing microorganisms at deep-sea hydrothermal vents. Since the microbial contribution to the nitrogen cycle at deep-sea hydrothermal vents remains largely unknown, this study is designed to fill this gap. Recent studies revealed the occurrence of novel thermophilic microorganisms that couple the reduction of nitrate with autotrophic CO2 fixation in marine geothermal environments. The ecological significance of such a microbial community at deep-sea vents is twofold: 1) these organisms contribute to the primary productivity by fixing CO2, and 2) their nitrate respiratory metabolism (namely, the reduction of NO3- to NO2-, N2, or NH4+) imply that nitrogen is conserved within the vent system and is recycled into the vent nitrogen cycle. This research will integrate novel cultivation and molecular techniques with stable isotope analyses to explore the physiology of nitrate-reducing microorganisms, and to assess their functional diversity and activity. By establishing a link between physiology, phylogeny and activity, this study will contribute to our understanding of the ecological relevance of nitrate-reducing organisms at deep-sea vents, as well as their contribution to both the carbon and nitrogen cycling. This research will also contribute to the expansion of the database of genes relevant to CO2 fixation and NO3- reduction, allowing for the improvement of detection tool for monitoring these microbial processes in the environment. Training opportunities will be offered to one graduate student and several undergraduate students, and educational and outreach activities associated with several NSF-sponsored programs (e.g., the Mid-Atlantic Center for Ocean Science Education Excellence and the Student Experiments at Sea) will be supported as well.