Collaborative Research: MIP: Physiology and molecular ecology of thermophilic nitrate-reducing microorgansisms at deep-sea hydrothermal vents

这项研究将调查深海热液喷口中嗜热、硝酸盐还原微生物的生理学和生态学。由于微生物对深海热液喷口氮循环的贡献在很大程度上尚不清楚，因此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，出现了将硝酸盐还原与自养二氧化碳固定相结合的新型嗜热微生物。深海喷口这种微生物群落的生态意义是双重的：1)这些生物通过固定二氧化碳来促进初级生产力，2)它们的硝酸盐呼吸代谢(即NO3-还原为NO2-、N2或NH4+)意味着氮在喷口系统中被保存并被循环到喷口氮循环中。这项研究将把新的培养和分子技术与稳定同位素分析相结合，探索硝酸盐还原微生物的生理，并评估它们的功能多样性和活性。通过建立生理、系统发育和活动之间的联系，这项研究将有助于我们理解深海喷口硝酸盐还原生物的生态相关性，以及它们对碳循环和氮循环的贡献。这项研究还将有助于扩大与二氧化碳固定和硝酸盐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。将为一名研究生和几名本科生提供培训机会，并将支持与NSF赞助的几个项目(例如，大西洋中部海洋科学教育卓越中心和学生海上实验)相关的教育和外联活动。

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.