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

氧气浓度对海洋生态系统的群落结构和功能有着重要影响。在低氧的沃茨，包括主要的海洋最低含氧区，生物多样性主要由复杂的微生物群落控制，其厌氧代谢调节全球氮和碳循环的关键步骤。令人惊讶的是，新的证据表明，OMZ还支持能够利用无机硫化合物进行能量代谢的各种微生物。这一组合似乎包括硫氧化自养和硫酸盐还原异养，表明一个活跃的硫循环与潜在的有机碳输入和矿化的重要作用，以及关键环节的OMZ氮循环。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、活性和地理分布在很大程度上仍未得到研究。该项目采用综合的分子和实验方法，严格审查的生理和系统发育的基础上微生物硫循环在氧气最低区。结合有针对性的宏基因组学与基因表达谱，微观世界硫添加实验和富集培养，PI将表征硫代谢微生物在两个海洋学和生态学上不同的低氧区域：东热带北太平洋（ETNP）OMZ墨西哥，这是世界上最大的永久OMZ，和季节性缺氧的“死亡区”在墨西哥湾（GOM）。具体地说，他们将测试以下假设：硫氧化和硫还原浮游细菌1）在ETNP OMZ中丰富且转录活跃，2）是缺氧GOM的次要组分，但当氧气减少和硫化物增加时，活性和丰度增加，3）在OMZ中，功能基因含量和垂直分布上的系统发育多样性表现出地理学变化，以及对环境梯度的响应。预计OMZ将扩大以应对未来的气候变化，因此必须全面了解低氧区域的生物学。该项目将建立一个全面的框架，用于研究OMZ中具有生态重要性但特征不明显的海洋浮游细菌功能群的基因组学和生理学。结果将相对于来自永久性东热带南太平洋（ETSP）OMZ和第二个季节性OMZ的现有宏基因组数据进行分析。（Saanich Inlet），从而为描述远洋硫的生态分布建立了比较基础-更广泛的影响海洋科学研究将作为一个平台，加强跨多个学术领域的科学教育，程度.海洋科学夏季研讨会（SWIMS）将与格鲁吉亚理工学院的K-12教育工作者和教师发展专家合作开发。为期5天的SWIMS计划，其中包括在海洋学的斯基达韦研究所2天，将从事研究生和格鲁吉亚技术研究人员在培训当地教师合并海洋科学的关键主题与新的国家标准在中学地球科学教育。此外，通过与莫尔豪斯学院和斯佩尔曼学院的伙伴关系，该项目资助暑期实习，以提高少数民族学生在本科海洋科学和生物信息学研究中的代表性。一个PI研究生工作组将在格鲁吉亚理工学院成立，以制定和实施海洋基因组学跨学科领域培训的新准则。格鲁吉亚理工学院将开设一门新课程，为科学家写作，以加强研究生的专业发展。它将使用结构化的，同行驱动的练习，使学生掌握在科学上取得成功所必需的关键写作和口语技能-这样的课程是严重缺乏格鲁吉亚理工学院。通过上述活动，该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，而且还将建立一个强大的基础，通过该基础，PI可以利用其工作成果来培训和激励未来的海洋科学家。

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.