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

知识价值。深海热液喷流沿6万km洋中脊系统分布于全球，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输入之间重要相互作用的宿主；热液能源刺激微生物活动和生产力的增强，微生物调节从深海热液喷口进入海洋的元素和能量的通量。这种热液通量是海洋中两种关键微量营养素铁和锰的重要来源。尽管如此，相对于那些居住在近喷口和地下环境中的微生物群落，深海热液羽流中的微生物群落研究不足。该项目的总体目标是揭示在深海热液柱中观察到的微生物活动增强和地球化学过程调解的微生物群落动态。该研究项目的重点是瓜伊马斯盆地（加利福尼亚湾）的羽流，先前的研究结果表明，相对于周围的深海，那里的微生物活动和酶促锰（II）氧化显著增强。尖端的DNA测序技术将通过宏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中获得的数十万个rRNA基因序列来比较羽流与背景中的群落结构和种群特异性活性；(2)从最丰富的深海微生物种群中重建复合基因组，并评估其代谢能力和营养需求；(3)定量比较羽流和背景中的基因含量和表达谱，重点揭示向趋化脂肪自养的代谢转变。总的来说，研究结果有望揭示羽流中微生物参与者和过程的本质：羽流生物地球化学是由热液输入刺激的本地深海微生物介导的，还是由来自近喷口环境的羽流特定群体介导的？更广泛的影响。该项目将在多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）和教师来研究一个跨学科的问题。其次，大规模环境DNA测序的统计和计算分析方法目前阻碍了新兴DNA测序技术的潜力，这些方法将得到改进，并通过开源程序、在线支持和文档向公众开放。第三，研究活动将与公共宣传活动密切结合。PI与密歇根大学IDEA研究所的教育专业人员之间的现有合作将扩大，为高中生开发一个地球科学夏令营。这个为期两周的夏令营将为来自密歇根州伊普斯兰蒂和底特律公立学校的高中生和教师提供实践经验和学习活动，这些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.