Collaborative Research: Antarctic Diatom Proteorhodopsins: Characterization and a Potential Role in the Iron-limitation Response

变形紫红质是嵌入在膜中的蛋白质，可以作为光驱动质子泵为新陈代谢和生长产生能量。在许多不同的海洋原核微生物中发现了变形紫质，对它们的分布和功能作用进行了广泛的研究。最近，在硅藻中发现了一种质子泵，视紫红质样基因，硅藻是一种海洋浮游植物，在南大洋的大部分地区占据着食物网的基础。从那时起，变形视紫红质已经在许多硅藻物种中被发现，但不是全部。与其他地区的硅藻相比，proteorhodopsin基因更常见于生活在海洋中寒冷、缺铁地区（包括南大洋）的硅藻中。人们认为变形紫质特别适合在南大洋中使用能源生产，因为它不需要铁，而且它的反应速率对温度不敏感（不像传统的光合作用）。该项目的总体目标是确定南极硅藻-变形紫质的特征，并确定其在这些硅藻适应南极水域低铁浓度和极低温中的作用。这项研究将为南大洋硅藻成功的遗传基础提供新的信息，以及这种独特的分子如何在为南极食物网的基础提供能量方面发挥关键作用。影响更广泛的活动旨在促进极地海洋科学相关专题的教学，将研究目标转化为中学生易于获得的教育材料。该项目将结合分子、生化和生理测量来确定变形紫质在南极半岛西部地区硅藻分离物中的作用和重要性。蛋白紫红质的质子泵送特性和泵送速率随光强和温度的变化，由此产生的蛋白紫红质的胞内ATP生产速率，以及蛋白的细胞定位将被确定。该项目将研究南极硅藻-变形紫质最高表达的环境条件，并构建在这些不同环境条件下生长的细胞能量预算，其中包括硅藻-变形紫质。对变形紫质产生的能量通量的估计将与光合光反应和代谢耦合呼吸速率产生的总能量进行比较。最后，将比较南极硅藻中硅藻-变形紫质和温带硅藻中含有变形紫质的硅藻分离物的特征和基因表达，以确定生活在海洋中寒冷、缺铁地区的硅藻是否优先依赖于通过变形紫质生产能源。教育活动将与莫尔黑德天文馆和科学中心合作进行，后者负责协调科学冒险项目，这是一个受教堂山及周边地区中学生欢迎的夏令营。在与天文馆的合作下，研究人员将为科学冒险的参与者开发一些活动，重点关注浮游植物及其在极地海洋食物网中的重要作用。此外，将为教室开发一个关于南极浮游植物的教学模块，提供给教育网络网站，并在全国科学教育工作者的讲习班上展示。该奖项反映了美国国家科学基金会的法定使命，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。

Proteorhodopsins are proteins that are embedded in membranes that can act as light-driven proton pumps to generate energy for metabolism and growth. The discovery of proteorhodopsins in many diverse marine prokaryotic microbes has initiated extensive investigation into their distributions and functional roles. Recently, a proton-pumping, rhodopsin-like gene was identified in diatoms, a group of marine phytoplankton that dominates the base of the food web in much of the Southern Ocean. Since this time, proteorhodopsins have been identified in many, but not all, diatom species. The proteorhodopsin gene is more frequently found in diatoms residing in cold, iron-limited regions of the ocean, including the Southern Ocean, than in diatoms from other regions. It is thought that proteorhodopsin is especially suited for use energy production in the Southern Ocean since it uses no iron and its reaction rate is insensitive to temperature (unlike conventional photosynthesis). The overall objective of the project is to characterize Antarctic diatom-proteorhodopsin and determine its role in the adaptation of these diatoms to low iron concentrations and extremely low temperatures found in Antarctic waters. This research will provide new information on the genetic underpinnings that contribute to the success of diatoms in the Southern Ocean and how this unique molecule may play a pivotal role in providing energy to the base of the Antarctic food web. Broader impact activities are aimed to promote the teaching and learning of polar marine-sciences related topics by translating research objectives into readily accessible educational materials for middle-school students.This project will combine molecular, biochemical and physiological measurements to determine the role and importance of proteorhodopsin in diatom isolates from the Western Antarctic Peninsula region. Proton-pumping characteristics and pumping rates of proteorhodopsin as a function of light intensity and temperature, the resultant proteorhodopsin-linked intracellular ATP production rates, and the cellular localization of the protein will be determined. The project will examine the environmental conditions where Antarctic diatom-proteorhodopsin is most highly expressed and construct a cellular energy budget that includes diatom-proteorhodopsin when grown under these different environmental conditions. Estimates of the energy flux generated by proteorhodopsin will be compared to total energy generation by the photosynthetic light reactions and metabolically coupled respiration rates. Finally, the characteristics and gene expression of diatom-proteorhodopsin in Antarctic diatoms and a proteorhodopsin-containing diatom isolates from temperate regions will be compared in order to determine if there is a preferential dependence on energy production through proteorhodopsin in diatoms residing in cold, iron-limited regions of the ocean. Educational activities will be performed in collaboration with the Morehead Planetarium and Science Center who co-ordinates the SciVentures program, a popular summer camp for middle-school students from Chapel Hill and surrounding areas. In collaboration with the Planetarium, the researchers will develop activities that focus on phytoplankton and the important role they play within polar marine food webs for the SciVentures participants. Additionally, a teaching module on Antarctic phytoplankton will be developed for classrooms and made available to educational networking websites and presented at workshops for science educators nationwide.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.