Mixotrophic bacteria and the cryptic marine sulfur cycle: Mechanisms of carbon assimilation and sulfur oxidation in the Arctic96BD-19 GSO clade

智力优势：海洋蕴藏着巨大的碳、氮、磷、硫和其他所有生命所需的元素。生活在海洋中的活跃和多样化的微生物种群负责调节维持海水化学的营养转化。最近的一项研究发现，Arctic96BD-19伽马蛋白细菌硫氧化物(GSO)谱系中存在一组无处不在的海洋细菌，该细菌与已知的硫氧化物种密切相关，这些硫氧化物种固定无机碳并在低氧水域氧化硫化物。GSO在含氧水域中使用还原形式硫的潜力表明，它们是连接海洋碳循环和硫循环的关键物种。Arctic96BD-19 GSO谱系中唯一已知的分离株现在正在培养中，这使得关于它们在碳和硫循环中所起作用的基本问题得到了研究。初步数据显示，它们利用硫磺氧化产生的能量吸收碳。该项目旨在解决一个重要的假设，即硫的转化为Arctic96BD-19谱系的GSO提供了在整个水柱中进行有机和无机碳循环的能量。我们将测试三个具体的假设。第96BD-19条细胞同化有机碳或固定无机碳，取决于环境条件。文章96BD-19细胞通过形成四硫酸盐中间体或使用分支的硫代硫酸盐氧化途径来氧化硫代硫酸盐。Arctic96BD-19细胞是普遍存在的硫氧化剂，通过太平洋西北部吸收有机和无机碳。将结合实验室对研究人员纯培养物的生长研究和比较基因组分析。基因组数据将用于确定Arctic96BD-19培养物是否具有将还原硫磺氧化为硫酸盐的遗传潜力(基于拥有已知的核心和辅助硫磺氧化基因)，使用哪些潜在的氧化途径，以及它们是否可以固定无机碳。这些数据将通过确定最有可能使用的无机和有机化合物的形式来帮助指导生理学研究。广泛的影响：海洋细菌在全球营养循环中发挥着关键作用，但它们在生态系统中的许多个体和群落功能还没有被很好地了解。未来的海洋学家将需要使用依赖于培养和不依赖于培养的方法来确定塑造微生物群落并影响生物地球化学循环的代谢过程。一名女研究生和两名本科生将接受使用分子和生理数据解决假说的培训。此外，该项目将通过数字电影向学生(特别是15至20岁的学生)介绍海洋研究的独特和令人兴奋的方面，从而增加全国对海洋科学的了解。华盛顿大学环境学院和艺术与科学学院之间的跨学院合作将培养数字媒体传播硕士学生，以制作短片，鼓励年轻人对海洋学感兴趣。学生教育、科学进步和公众意识都是这个项目的重要组成部分。

Intellectual merit: The ocean serves an immense reservoir of carbon, nitrogen, phosphorus, sulfur, and other elements required for all life. The active and diverse microbial populations that inhabit the oceans are responsible for mediating nutrient transformations that maintain the chemistry of seawater. A recent study identified a ubiquitous group of marine bacteria from the Arctic96BD-19 gamma-proteobacterial sulfur oxidizer (GSO) lineage that is closely related to known sulfur oxidizing species that fix inorganic carbon and oxidize sulfide in low-oxygen waters. The potential for GSOs to use reduced forms of sulfur in oxygenated waters suggests that they are a keystone species that link the marine carbon and sulfur cycles. The only known isolates from the Arctic96BD-19 lineage of GSOs are now in culture, allowing fundamental questions about their roles in carbon and sulfur cycling to be investigated. Preliminary data suggest that they use energy from the oxidation of sulfur to assimilate carbon. This project seek to address the overarching hypothesis that sulfur transformations provide the Arctic96BD- 19 lineage of GSOs with energy for organic and inorganic carbon cycling throughout the water column. Three specific hypotheses will be tested.1. Arctic96BD-19 cells assimilate either organic carbon or fixes inorganic carbon, depending on environmental conditions.2. Arctic96BD-19 cells oxidize thiosulfate via formation of a tetrathionate intermediate, or using the branched thiosulfate oxidation pathway.3. Arctic96BD-19 cells are ubiquitous sulfur oxidizers that assimilate organic and inorganic carbon through the Pacific Northwest.A combination of laboratory growth studies of the investigator's pure cultures and comparative genomic analyses will be used. The genomic data will be used to determine whether the Arctic96BD-19 cultures possess the genetic potential to oxidize reduced sulfur to sulfate (based on possession of known core and ancillary sulfur oxidation genes), which potential oxidation pathways are used, and whether they can fix inorganic carbon. These data will help guide the physiology studies by determining the most likely forms of inorganic and organic compounds that can be utilized.Broader impacts: Marine bacteria are critical players in global nutrient cycles, but many of their individual and community functions in the ecosystem are not well understood. Future oceanographers will need to use cultivation-dependent and cultivation-independent methods to identify metabolic process that shape microbial communities and impact biogeochemical cycles. A female graduate student and two undergraduate students will be trained to use molecular and physiological data to address hypotheses. Additionally, this project will increase national exposure of ocean sciences through digital films that introduce students (particularly ages 15 to 20) to unique and exciting aspects of oceanographic research. A cross-college collaboration between the UW College of the Environment and the College of Arts and Sciences will train Master of Communication in Digital Media students to produce short films that encourage interest in oceanography among young people. Student education, scientific advancement, and public awareness are all important components of this project.