CAREER: A phylogenetic and functional understanding of microbial sulfur cycling in oxygen minimum zones

职业：对最低氧区微生物硫循环的系统发育和功能理解

• 批准号: 1151698
• 负责人: Frank Stewart
• 金额: $ 121.09万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-02-15 至 2020-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1151698&HistoricalAwards=false
• 关键词: CAREER; phylogenetic; functional; understanding; microbial

Oxygen concentration significantly impacts the community structure and function of marine ecosystems. In waters with low oxygen, including the major marine oxygen minimum zones (OMZs), biological diversity is dominated by a complex community of microorganisms whose anaerobic metabolisms mediate key steps in global nitrogen and carbon cycles. Surprisingly, new evidence indicates that OMZs also support diverse microorganisms capable of utilizing inorganic sulfur compounds for energy metabolism. This assemblage appears to include both sulfur-oxidizing autotrophs and sulfate-reducing heterotrophs, suggesting an active sulfur cycle with potentially substantial roles in organic carbon input and mineralization, as well as critical links to the OMZ nitrogen cycle. Our knowledge of the microorganisms driving OMZ sulfur cycling is based largely on the metagenome of a single bacterial lineage (SUP05) and on surveys of diagnostic marker genes, which have thus far targeted only a subset of the diverse low-oxygen regions in the global ocean. The metabolic diversity, activity, and biogeographic distribution of sulfur-metabolizing microorganisms in the OMZ water column remain largely unexplored. This project uses an integrated molecular and experimental approach to critically examine the physiological and phylogenetic basis of microbial sulfur cycling in oxygen minimum zones. Combining targeted metagenomics with gene expression profiling, microcosm sulfur-addition experiments, and enrichment culturing, the PI will characterize sulfur-metabolizing microorganisms in two oceanographically and ecologically distinct low-oxygen regions: the Eastern Tropical North Pacific (ETNP) OMZ off Mexico, which represents the largest permanent OMZ in the world, and the seasonally hypoxic "dead zone" in the Gulf of Mexico (GOM). Specifically, they will test the hypotheses that sulfur- oxidizing and -reducing bacterioplankton 1) are abundant and transcriptionally active in the ETNP OMZ, 2) are minor components of the hypoxic GOM, but increase in activity and abundance when oxygen decreases and sulfide increases, and 3) exhibit biogeographic variation in functional gene content and phylogenetic diversity over vertical profiles, among OMZs, and in response to environmental gradients. OMZs are predicted to expand in response to future climate change, making it imperative to holistically understand the biology of low-oxygen regions. This project will establish a comprehensive framework for studying the genomics and physiology of an ecologically important, but poorly characterized, functional group(s) of marine bacterioplankton in OMZs. Results will be analyzed relative to existing metagenomic data from the permanent Eastern Tropical South Pacific (ETSP) OMZ, and a second seasonal OMZ (Saanich Inlet), thereby establishing a comparative basis for describing the ecological distribution of pelagic sulfur-metabolizing microorganisms and their relative role in OMZ community metabolism.Broader ImpactsMarine science research will be used as a platform for enhancing science education across multiple academic levels. A Summer Workshop in Marine Science (SWIMS) will be developed in collaboration with K-12 educators and teacher-development experts at Georgia Tech. The 5-day SWIMS program, which includes 2 days at the Skidaway Institute of Oceanography, will engage graduate students and Georgia Tech researchers in training local teachers to merge key topics in marine science with new national standards in middle school Earth Science education. In addition, through a partnership with Morehouse and Spelman Colleges, this project funds summer internships to enhance representation of minority students in undergraduate marine science and bioinformatics research. A PI-graduate student working group is to be established at Georgia Tech to develop and implement new guidelines for training in the cross-disciplinary field of marine genomics. A new course will be created at Georgia Tech, Writing for Scientists, to enhance the professional development of graduate students. It will use structured, peer-driven exercises to equip students with the critical writing and speaking skills necessary for success in science - such a course is critically lacking at Georgia Tech. Through the activities outlined above, this CAREER project will not only establish a research group dedicated to characterizing an ecologically significant, but cryptic, component of the marine microbial ecosystem, but will also develop a strong foundation through which the PI can use the results of his work to train and motivate future generations of marine scientists.

氧气浓度显着影响海洋生态系统的群落结构和功能。在低氧水域，包括主要的海洋最低氧区（OMZ），生物多样性由复杂的微生物群落主导，这些微生物的无氧代谢介导全球氮和碳循环的关键步骤。令人惊讶的是，新证据表明 OMZ 还支持多种能够利用无机硫化合物进行能量代谢的微生物。该组合似乎包括硫氧化自养生物和硫酸盐还原异养生物，表明活跃的硫循环在有机碳输入和矿化中具有潜在的重要作用，并且与 OMZ 氮循环具有重要联系。我们对驱动 OMZ 硫循环的微生物的了解主要基于单一细菌谱系 (SUP05) 的宏基因组和诊断标记基因的调查，迄今为止，这些基因仅针对全球海洋中不同低氧区域的一个子集。 OMZ 水体中硫代谢微生物的代谢多样性、活性和生物地理分布在很大程度上仍未得到探索。该项目采用综合分子和实验方法来严格研究最低氧区域微生物硫循环的生理和系统发育基础。将目标宏基因组学与基因表达谱、微观加硫实验和富集培养相结合，PI 将描述两个海洋学和生态学上不同的低氧区域中硫代谢微生物的特征：墨西哥附近的东部热带北太平洋 (ETNP) OMZ，该区域代表了世界上最大的永久性 OMZ，以及墨西哥湾 (GOM) 的季节性缺氧“死亡区”。具体来说，他们将测试以下假设：氧化硫和还原硫的浮游细菌 1) 在 ETNP OMZ 中丰富且具有转录活性，2) 是缺氧 GOM 的次要成分，但当氧气减少和硫化物增加时，其活性和丰度会增加， 3）在垂直剖面、OMZ 之间以及对环境梯度的响应中，表现出功能基因内容和系统发育多样性的生物地理变化。预计 OMZ 会因未来气候变化而扩大，因此必须全面了解低氧区域的生物学。该项目将建立一个综合框架，用于研究 OMZ 中具有重要生态意义但特征尚不清楚的海洋浮游细菌功能群的基因组学和生理学。将根据来自永久东部热带南太平洋（ETSP）OMZ和第二个季节性OMZ（萨尼奇湾）的现有宏基因组数据对结果进行分析，从而为描述中上层硫代谢微生物及其相关微生物的生态分布建立比较基础更广泛的影响海洋科学研究将被用作加强多个学术层面的科学教育的平台。将与佐治亚理工学院的 K-12 教育工作者和教师发展专家合作举办海洋科学夏季研讨会 (SWIMS)。为期 5 天的 SWIMS 项目，其中包括在斯基德威海洋研究所的 2 天，将让研究生和佐治亚理工学院的研究人员参与培训当地教师，将海洋科学的关键主题与中学地球科学教育的新国家标准相结合。此外，通过与莫尔豪斯学院和斯佩尔曼学院合作，该项目资助暑期实习，以提高少数族裔学生在本科海洋科学和生物信息学研究中的代表性。佐治亚理工学院将成立一个 PI 研究生工作组，负责制定和实施海洋基因组学跨学科领域培训的新指南。佐治亚理工学院将开设一门新课程“为科学家写作”，以促进研究生的专业发展。它将使用结构化的、同伴驱动的练习来培养学生在科学领域取得成功所必需的批判性写作和口语技能——佐治亚理工学院严重缺乏这样的课程。通过上述活动，这个职业项目不仅将建立一个研究小组，致力于表征海洋微生物生态系统中具有生态意义但神秘的组成部分，而且还将建立一个坚实的基础，通过该基础，PI可以利用他的研究成果致力于培训和激励下一代海洋科学家。