Effects of Climate Change Variables on Microbial Autotroph-Heterotroph Carbon Flux

海洋表面的浮游植物负责地球上大约一半的光合作用。这些光合生物产生的大部分有机物质最终被不同的海洋细菌消耗，这些细菌对特定类型的化合物有不同的偏好。该项目调查气候变化（温度和二氧化碳）如何改变不同种类的海洋浮游植物产生的有机化合物的类型和数量，以及从浮游植物转移到海洋细菌的化合物的类型和数量。转移到细菌中的有机化合物的变化可能会改变海洋中细菌物种的分布，它们的生长速度和效率，以及全球海洋中的能量流动。该项目帮助科学家更好地了解气候变化对海洋生态系统的影响。该项目支持两名研究生和一名博士后研究员，接受生物学，化学和海洋科学的跨学科培训。PI实验室的暑期研究实习提供给就读于佐治亚州雅典Cedar Shoals高中的AP生物学学生，这所学校为多样化的社会和经济社区提供服务。海洋表面的大部分细菌次级生产都是通过快速吸收浮游植物释放的不稳定代谢物来支持的，无论是直接通过排泄和扩散，还是间接通过溶解和捕食。该项目调查了两个气候变化变量（温度和二氧化碳）对三种模式浮游植物（硅藻，颗石藻和蓝藻）产生和释放的代谢物池的影响，并评估了转移到细菌的代谢物的组成和命运的变化。浮游植物物种生长axenically在两个不同的温度和CO2浓度的析因设计和endo-和exometabolite组合物使用NMR测定。一套浮游植物的生理特性的测量和评价的背景下，代谢物的组成。目前正在进行异养细菌（模式细菌或自然细菌群落）实验，以评估气候变化变量对浮游植物向海洋细菌转移代谢物的影响。在第一类实验中，细菌与浮游植物在不同温度和CO2浓度下共培养，细菌基因表达和代谢物浓度的变化被用来评估转移的代谢物组成的变化。在第二种类型中，细菌生长在高通量生物测定中不同温度和CO2浓度下产生的浮游植物代谢物池中，不同气候情景导致的细菌特性（生长速率、承载能力、生长效率）的变化用于指示代谢物质量的变化。了解浮游植物代谢物的异养过程如何随着气候变化而变化，可以更好地预测地球未来的碳循环。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Phytoplankton in the surface ocean are responsible for roughly half of all photosynthesis on the planet. Much of the organic material created by these photosynthetic organisms is ultimately consumed by diverse marine bacteria with differing preferences for specific types of chemical compounds. This project investigates how climate change (temperature and CO2) might alter the types and amounts of organic compounds produced by different species of marine phytoplankton and the types and amounts of compounds transferred from phytoplankton to marine bacteria. Shifts in organic compounds transferred to bacteria could alter the distribution of bacterial species in the ocean, their growth rates and efficiencies, and flows of energy through the global ocean. This project helps scientists better understand the effects of climate change on marine ecosystems. Two graduate students and a postdoctoral researcher are supported by the project, receiving interdisciplinary training in biology, chemistry, and ocean sciences. Summer research internships in the PIs’ laboratories are offered to AP Biology students enrolled at Cedar Shoals High School in Athens, GA, a school that serves a diverse social and economic community.Much of the bacterial secondary production in the surface ocean is supported by rapid uptake of labile metabolites released from phytoplankton, either directly through excretion and diffusion or indirectly through lysis and predation. This project investigates the effects of two climate change variables (temperature and CO2) on the metabolite pools produced and released by three model phytoplankton species (a diatom, a coccolithophore, and a cyanobacterium) and assesses changes in the composition and fate of metabolites transferred to bacteria. Phytoplankton species are being grown axenically at two different temperatures and CO2 concentrations in a factorial design and endo- and exometabolite composition is determined using NMR. A suite of phytoplankton physiological characteristics is measured and evaluated in the context of metabolite composition. Experiments with heterotrophic bacteria (either model bacteria or natural bacterial communities) are being conducted to assess the effects of climate change variables on metabolite transfer from phytoplankton to marine bacteria. In the first experiment type, bacteria are co-cultured with the phytoplankton at different temperatures and CO2 concentrations, and changes in bacterial gene expression and metabolite concentrations are used to assess shifts in the composition of metabolites transferred. In the second type, bacteria are grown on phytoplankton metabolite pools produced at different temperatures and CO2 concentrations in high-throughput bioassays, and changes in bacterial traits (growth rate, carrying capacity, growth efficiency) resulting from the different climate scenarios are used to indicate changes in metabolite quality. Knowledge of how the heterotrophic processing of phytoplankton metabolites might shift in response to climate change allows better prediction of Earth's future carbon cycle.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.