OCE-PRF Track 1 (Broadening Participation): Impact of Phytoplankton-Bacteria Interactions on Metal Bioavailability

在为期两年的博士后研究中，该研究员将分析细菌-浮游植物相互作用如何影响沙漠尘埃中微量金属的利用。这些实验结果将阐明金属螯合剂的产生所带来的生物学优势，因为它揭示了细菌在浮游植物金属获取中的作用，并将促进对海洋初级生产和碳循环的理解。该研究员将通过以海洋科学和海洋微量金属营养为重点的教学模块和研究实习，扩大在当地高中和多元化服务大学中代表性不足的群体对海洋科学的参与。该研究员由伍兹霍尔海洋研究所的赞助科学家Mak Saito博士主持。该研究探讨了细菌和浮游植物之间的相互作用如何调节沙漠尘埃中金属的生物利用度，从而影响金属的吸收和浮游植物的生长。这项工作提出了以下假设：浮游植物培养物中细菌的存在将(a)促进铁和钴的增溶，(b)刺激浮游植物对金属的吸收和生长，(c)导致铁吸收转运蛋白的表达，这与它们在自然海洋环境中的表达更接近。具体来说，微真核生物Ostreococcus和鳄鱼蓝细菌Crocosphaera将在无菌条件下（对照）、分离细菌（实验室培养实验）和存在天然细菌群体（船上培养实验）、添加或不添加沙漠尘埃、在微量金属清洁条件下进行半连续培养。Ostreococcus和Crocosphaera是微真核光合作用和固氮过程的典型模式生物。处理对生长速率、金属摄取和配体条件稳定常数的影响将被测量。铁载体转运体和其他参与铁摄取的蛋白质将通过蛋白质组学方法检测。此外，差异和定量蛋白质组学方法将允许检测涉及地下海洋样品中铁摄取的蛋白质，以便与实验培养物的转运蛋白和转运蛋白表达水平进行比较。

In this two year postdoctoral research fellowship, the fellow will analyze how bacteria-picophytoplankton interactions impact the utilization of trace metals from desert dust. Results of these experiments will elucidate biological advantages conferred by the production of metal chelators, as it reveals the role that bacteria play in phytoplankton metal acquisition, and will advance understanding in oceanic primary production and carbon cycling. The fellow will broaden participation of under-represented groups in ocean sciences at local high schools and diversity-serving colleges through teaching modules and research internships focusing on the ocean sciences and marine trace metal nutrition. The fellow is being hosted by sponsoring scientist Dr. Mak Saito at Woods Hole Oceanographic Institution.The research examines how the interactions between bacteria and phytoplankton modulate the bioavailability of metals from desert dust, and thus impact metal uptake and the growth of phytoplankton. The work addresses the following hypothesis: The presence of bacteria in picophytoplankton cultures will (a) enable iron and cobalt solubilization, (b) spur picophytoplankton metal uptake and growth, and (c) lead to expression of iron uptake transporters which more closely resembles their expression in the natural marine environment. Specifically, the picoeukaryote Ostreococcus and the cyanobacterium Crocosphaera will be grown in semi-continuous cultures under axenic conditions (control), with bacterial isolates (laboratory culture experiments) and in the presence of natural bacterial populations (shipboard culture experiments), with and without addition of desert dust, under trace metal clean conditions. Ostreococcus and Crocosphaera are representative model organisms for processes of picoeukaryotic photosynthesis and nitrogen fixation. Treatment effects on growth rate, metal uptake, and ligand conditional stability constants will be measured. Siderophore transporters and other proteins involved in iron uptake will be detected by proteomic methods. Further, a differential and quantitative proteomic approach will allow for the detection of proteins involved in iron uptake in subsurface ocean samples, in order to compare to the transporters and transporter expression levels of experimental cultures.