Linking biogeochemistry and microbial community dynamics in deep-sea hydrothermal plumes

智力上的优点。深海热液喷口羽流沿6万公里的大洋中脊系统分布在全球，是深海微生物生物地球化学研究的热点。这些羽流是微生物群落和热液投入之间重要相互作用的场所；热液能源刺激提高微生物的活动和生产力，微生物调节深海热液喷口向海洋的元素和能量流动。这种热液通量是海洋中两种关键的微量营养素--铁和锰--的重要来源。尽管有这样的重要性，深海热液羽流中的微生物群落相对于生活在喷口附近和地下环境中的微生物群落的研究一直不足。该项目的总体目标是揭示在深海热液羽流中观察到的微生物群落动态对微生物活动的增强和对地球化学过程的调解作用。这一研究项目的重点是瓜伊马斯盆地(加利福尼亚州海湾)的羽流，此前的结果显示，与周围深海相比，那里的微生物活动和酶促锰(II)氧化作用显著增强。尖端的DNA测序技术将被用来通过元基因组学和元转录组学来表征羽流与背景群落的微生物多样性、代谢潜力和生理状态。具体目标是(1)利用从DNA和RNA中获得的数十万rRNA基因序列来比较羽流中的群落结构和种群特异性活动与背景；(2)从最丰富的深海微生物种群中重建复合基因组，并评估它们的代谢能力和营养需求；以及(3)定量比较羽流和背景中的基因含量和表达谱，重点是揭示向化学自养的代谢转变。总体而言，预计结果将阐明羽流中微生物行为者和过程的性质：羽流生物地球化学是由受到热液输入刺激的本地深海微生物所调节的，还是由来自喷口附近环境的特定羽流群体所调节的？该项目将在几个层面产生广泛影响。首先，这项研究将汇集来自地球科学、微生物生态学和生物信息学的学生(本科生和研究生)和教职员工，以调查一个跨学科的问题。其次，目前阻碍新兴DNA测序技术潜力的大规模环境DNA测序的统计和计算分析方法将得到改进，并通过开放源码程序、在线支持和文档公开可用。第三，研究活动将与公众宣传活动密切结合。PI和密歇根大学IDEA研究所的教育专业人员之间的现有合作将扩大，以开发一个面向高中生的地球科学夏令营。为期两周的夏令营将为来自密歇根州伊普西兰蒂和底特律公立学校的高中生和教师提供实践体验和学习活动，这两所学校是许多来自代表性不足群体的潜在未来科学家的家园。

Intellectual merit. Deep-sea hydrothermal vent plumes are globally distributed along the 60,000-km mid-ocean ridge system and are hot spots of microbial biogeochemistry in the deep oceans. These plumes play host to important interactions between microbial communities and hydrothermal inputs; hydrothermal energy sources stimulate enhanced microbial activity and productivity, and microorganisms mediate the flux of elements and energy from deep-sea hydrothermal vents into the oceans. This hydrothermal flux is a significant source of two key micronutrients, iron and manganese, for the oceans. Despite this importance, microbial communities in deep sea-hydrothermal plumes have been understudied relative to those inhabiting near-vent and subsurface environments. The overall goal of this project is to reveal the microbial community dynamics responsible for enhanced microbial activities and mediation of geochemical processes that has been observed in deep-sea hydrothermal plumes. This research project is focused on plumes in the Guaymas Basin (Gulf of California), where previous results showed dramatic enhancement of microbial activity and enzymatic manganese (II) oxidation relative to the ambient deep sea. Cutting-edge DNA sequencing technologies will be utilized to characterize the microbial diversity, metabolic potential and physiological state of plume versus background communities through metagenomics and metatranscriptomics. The specific objectives are (1) to utilize hundreds of thousands of rRNA gene sequences available from DNA and RNA to compare community structure and population-specific activity in plumes versus background; (2) to reconstruct composite genomes from the most abundant deep-sea microbial populations and evaluate their metabolic capabilities and nutritional needs; and (3) to quantitatively compare gene content and expression profiles in plume and background, with a focus on uncovering metabolic shifts towards chemolithoautotrophy. Overall, results are expected to shed light on the nature of microbial players and processes in plumes: is plume biogeochemistry mediated by indigenous deep-sea microorganisms that have been stimulated by hydrothermal inputs, or by plume-specific groups that were entrained from near-vent environments?Broader impacts. The project will have broad impacts at several levels. First, the research will bring together students (undergraduate and graduate) and faculty from geosciences, microbial ecology, and bioinformatics to investigate an interdisciplinary problem. Second, methods for statistical and computational analysis of large-scale environmental DNA sequencing that are currently hindering the potential of emerging DNA sequencing technologies will be advanced and made publicly accessible with open source programs, online support, and documentation. Third, research activities will be intimately integrated into public outreach activities. An existing collaboration between the PI and education professionals at the University of Michigan's IDEA Institute will be expanded to develop a summer camp in the geosciences for high school students. This two-week summer camp will enable hands-on experiences and learning activities for high school students and teachers from Ypsilanti and Detroit, MI public schools, which are home to many potential future scientists from underrepresented groups.