Collaborative Research: Geochemical Effects on the Functional Microbial Community Dynamics of Hydrothermal Deposits along the Eastern Lau Spreading Center

深海热液喷口存在极端的环境梯度，高温、低pH值和减少的液体与冷的含氧海水混合。这导致大量微生物利用丰富的微生态位。通过小亚基 (16S) rRNA 基因调查和对许多地点喷口沉积物的定向富集培养，多样性模式正在出现，表明地球化学过程，特别是影响流体 pH 值的地球化学过程，在调节微生物多样性和群落组成方面发挥着重要作用。这是一项为期三年的研究，在东部刘扩散中心 (ELSC) 沿线的喷口场进行，旨在调查喷口地球化学与微生物群落动态之间的关系。之所以选择 ELSC，是因为它在流体和岩石地球化学、扩散速率、岩浆/构造过程以及相对较短的 397 公里长度上接近火山弧方面提供了巨大且系统的变化。因此，各个喷口场为深入探索影响与积极形成深海热液矿床相关的微生物群落多样性和关系的因素提供了极好的自然实验室。该研究将在 ELSC 沿线的 3 个地球化学性质不同的热液田进行。科学家们将记录每个地区与热液矿床相关的微生物群落组成和多样性，以便与 2009 年和 2005 年获得的数据进行比较。ELSC 内这些地球化学上不同的喷口区域的紧密接近提供了一个理想的机会，以研究喷口流体和沉积物地球化学对微生物群落结构和功能的影响，以及与活跃热液矿床相关的个体种群的具体作用。研究人员假设，考虑到极端的环境特征（例如，Mariner 的低流体 pH 值和高铁含量），他们将看到基洛莫阿纳、ABE 和 Mariner 喷口场之间的宏基因组，特别是元转录组存在明显差异。具体目标是： 1) 将 ELSC 沿线的地​​球化学和微生物动力学联系起来（2005-2013 年）； 2）利用宏基因组和转录组数据探索生物地球化学循环，这些循环调节着ELSC沿线喷口场中微生物群落的功能作用； 3) 使用宏基因组信息来富集靶向新型 Thermoprotei 和嗜酸菌。将从 ELSC 沿线的喷口场收集活性热液金属硫化物沉积物和流体样本。将获得 80 多个样本的古细菌和细菌 16S rRNA 扩增子的条形码焦磷酸测序。将模拟烟囱的地球化学环境以确定原位地球化学条件。这些值将用于统计分析，以探索影响社区中观察到的差异的因素。使用 16S rRNA 基因 454 热标记与地球化学表征相结合，将选择特定样本进行宏基因组和宏转录组分析（每个位点各 1-3 个）。分子信息将用于针对以下特定样本：（i）具有新颖的未分类多样性； (ii) 具有通风口地方病谱系； (iii) 具有来自陆地系统的嗜酸亲戚，用于富集培养（利用地球化学来帮助限制培养条件）。更广泛的影响。该项目将扩大我们对微生物生物圈范围的了解。至少一名研究生将参与涉及下一代测序、分子微生物生态技术和地球化学建模的跨学科研究。 ALR 将让一名已注册的 PSU 太平洋岛民学生参与研究并请求研究巡航。布里奇沃特州立大学的本科生将参与流体采样项目，从而提供有意义且令人兴奋的研究体验。 PI 将通过撰写一般性文章、在学校举办讲座以及通过现有计划（例如通过周六学院 (PSU) (http://www.saturdayacademy.org/)）对学校教师进行继续教育，与公众分享新的深海喷口发现的兴奋。

Extreme environmental gradients exist at deep-sea hydrothermal vents where high temperature, low pH and reduced fluids mix with cold oxygenated seawater. This results in a plethora of microbes taking advantage of abundantly available microniches. From small subunit (16S) rRNA gene surveys and directed enrichment culturing of vent deposits from many sites, patterns in diversity are emerging that suggest that geochemical processes, particularly those that affect fluid pH, play a fundamental role in regulating microbial diversity and community composition. This a three year study at vent fields along the Eastern Lau Spreading Center (ELSC) to investigate the relationship between vent geochemistry and microbial community dynamics. The ELSC was chosen because it provides large and systematic changes in fluid and rock geochemistry, spreading rate, magmatic/tectonic processes, and proximity to the volcanic arc over its relatively short length of 397 km. The individual vent fields therefore provide excellent natural laboratories for exploring, in depth, the factors that influence the diversity and relationships of microbial communities associated with actively forming deep-sea hydrothermal deposits. The study will be carried out at 3 geochemically different hydrothermal fields along the ELSC. The scientists will document microbial community composition and diversity associated with hydrothermal deposits from each area for comparison with data obtained in 2009 and 2005. The close proximity of these geochemically distinct vent areas within the ELSC provides an ideal opportunity to investigate the effect of vent fluid and deposit geochemistry on the structure and function of microbial communities, as well as the specific roles of individual populations, associated with active hydrothermal deposits. The investigators hypothesize that, given the extreme environmental characteristics (e.g., low fluid pH and high iron at Mariner), they will see distinct differences in the metagenomes and particularly in the metatranscriptomes among the Kilo Moana, ABE and Mariner vent fields. The specific objectives are to: 1) Link geochemical and microbial dynamics along the ELSC (from 2005-­2013); 2) Use of metagenomic and transcriptomic data to explore biogeochemical cycles that are regulating the functional roles of the microbial communities in vent fields along the ELSC; and 3) Use the metagenomic information to enrich for targeted novel Thermoprotei and acidophiles. Active hydrothermal metal sulfide deposits and fluid samples will be collected from the vent fields along the ELSC. Bar-coded pyrosequencing of archaeal and bacterial 16S rRNA amplicons will be obtained for over eighty samples. The geochemical environment of the chimneys will be modeled to determine in situ geochemical conditions. These values will be used in statistical analyses to explore the factors affecting the observed differences in the communities. Using the 16S rRNA gene 454 pyrotags coupled with the geochemical characterization, specific samples will be selected for metagenomic and metatranscriptomic analyses (1-3 of each per site). The molecular information will be used to target specific samples that: (i) harbor novel unclassified diversity; (ii) have vent endemic lineages; and (iii) have acidophilic relatives from terrestrial systems, for enrichment culturing (using the geochemistry to help constrain culturing conditions). Broader Impacts. The project will expand our understanding of the extent of the microbial biosphere. At least one graduate student will participate in interdisciplinary studies that involve next-­generation sequencing, molecular microbial ecological techniques, and geochemical modeling. ALR will involve a registered PSU Pacific Islander student in the research and requested research cruise. Undergraduate students from Bridgewater State University will be involved in the fluid sampling program, thereby providing a meaningful and exciting research experiences. The PIs will share the excitement of new deep-sea vent discoveries with the public through writing general articles, giving lectures at schools, and through continuing education for school teachers through existing programs (e.g. through the Saturday Academy, PSU (http://www.saturdayacademy.org/).