Collaborative Research: Evolution of Early Metabolism: Carbon Fixation, Anaerobic Respiration and ROS Detoxification in the Anaerobic Vent Bacterium, Thermovibrio ammonificans

可以在没有氧气的情况下生存的细菌(厌氧菌)和在炎热环境中生存的细菌(嗜热菌)生活在极端环境中，例如类似早期地球的深海热液喷口。这些现代细菌与我们的星球共同进化，因此，这些生物携带着祖先和最近获得的基因，可以作为重建微生物过程进化的模型，包括这些细菌如何获得生长所需的能量和碳。为了深入了解这些过程，将对生活在深海热液喷口的一种生物--氨热杆菌进行研究。这些研究将纳入针对初中生和高中生的外展活动。课程计划将被开发并用于课外计划、K-12教育工作者的专业培训计划以及非正式活动，如4-H暑期科学计划。从生态学的角度来看，深海热液喷口中的厌氧化学自养细菌至关重要；它们在无氧的情况下固定地热/岩浆来源的二氧化碳，是这些环境中的主要生产者。该项目将通过利用不同类型的培养方法(分批和连续培养)以及模式生物-氨热杆菌的比较基因组分析，深入了解早期和获得性细菌新陈代谢的演变。实验将讨论氨毛虫在地球上的早期祖先是否最初是一种氢氧化、硫还原细菌，这种细菌可以从简单的无机物(如二氧化碳)形成所需的有机物质。随着大气中氧气的逐渐增加，更有效的末端电子受体变得可用，这种细菌获得了增加其代谢灵活性的基因--例如，利用硝酸盐和二氧化碳的能力--同时保留了祖先的代谢特征(如在没有氧气的情况下生存和在高温下生存的能力)。将结合转录学、蛋白质组学和生物量碳稳定同位素分析来研究氨毛虫的固碳、厌氧呼吸和活性氧的解毒机制。这项研究将提供有关氨毛虫在化学和营养条件下生长的基因表达的宝贵信息，尽可能准确地反映其自然环境中遇到的基因表达，并将为基因调控和表达对不断变化的环境条件的反应提供洞察。这项研究有望帮助重建这种深分支生物体的祖先和后天代谢特征，并揭示自养固碳途径的出现和进化。

Bacteria that can live without oxygen (anaerobes) and survive in hot environments (thermophiles) inhabit extreme environments such as deep-sea hydrothermal vents that resemble the early Earth. These modern-day bacteria co-evolved with our planet, and as a result, these organisms carry both ancestral and more recently acquired genes and can be used as models to reconstruct the evolution of microbial processes, including how these bacteria obtained energy and the carbon needed to grow. To gain insight into these processes Thermovibrio ammonificans, an organism that inhabits deep-sea hydrothermal vents, will be studied. Integrated into these studies will be outreach activities for middle and high school students. Lesson plans will be developed and used in after-school programs, in professional training programs for K-12 educators, and informal activities such as the 4-H Summer Science Program. Anaerobic chemolithoautotrophic bacteria inhabiting deep-sea hydrothermal vents are critically important from an ecological standpoint; by fixing carbon dioxide of geothermal/magmatic origin in the absence of oxygen, they are the primary producers in these environments. This project will provide insight into the evolution of early and acquired bacterial metabolism by leveraging different types of culture approaches (batch and continuous cultures) with comparative genomic analyses of the model organism, Thermovibrio ammonificans. Experiments will address whether an early Earth ancestor of T. ammonificans was originally a hydrogen-oxidizing, sulfur-reducing bacterium that could form needed organic substances from simple inorganic substances (such as carbon dioxide). With the gradual rise of oxygen in the atmosphere, more efficient terminal electron acceptors became available and this bacterium acquired genes that increased its metabolic flexibility - e.g., the capacity to use nitrate as well as carbon dioxide - while retaining ancestral metabolic traits (such as the ability to live without oxygen and survive high temperatures). The mechanisms of carbon fixation, anaerobic respiration and detoxification of reactive oxygen species in T. ammonificans will be investigated using a combination of transcriptomic, proteomic and biomass carbon stable isotope analyses. This study will provide invaluable information on gene expression in T. ammonificans grown under chemical and nutrient conditions that reflect, as closely as possible, those encountered in its natural environment and will provide insight on gene regulation and expression in response to changing environmental conditions. This study is anticipated to help reconstruct the ancestral and acquired metabolic traits of this deep-branching organism and shed light into the emergence and evolution of autotrophic carbon fixation pathways.