Ammonia Oxidation Versus Heterotrophy in Crenarchaeota Populations from Marine Environments West of the Antarctic Peninsula

氨氧化是再生氮转化为二氮气体的第一步，这是一个由三种不同的细菌和古细菌介导的三步途径。在气候变化对生物地球化学速率的影响可能很明显的极地海洋中，氨氧化和整个硝化-反硝化过程受到的关注相对较少。此前在南极半岛西部Palmer LTER研究区（WAP）对氨氧化古菌（AOA）的研究表明，crenarchaeote代谢具有强烈的垂直分异，“冬季水域”（WW， ~50-100 m深度范围）以非AOA的crenarchaeotes为主，而位于冬季水域（150-3500 m）以下的“环极深水”（CDW）的Crenarchaeota种群以AOA为主。对来自北冰洋的有限样本的分析并没有显示出AOA的垂直分离，并表明那里的AOA和绿原藻的丰度远低于南极。这些发现导致了本项目将检验的3个假设：1)北冰洋样品中绿古藻和AOA的明显低丰度可能是由于种群的空间或时间变异；2) WAP中绿原藻WW居群以异养优势居群；3)该水团形成后，WAP中绿原藻WW种群在春夏季“生长”。该研究将通过提供对AOA生态学和生理学的见解，为了解Palmer LTER（长期生态研究）研究区域氮循环的一个重要方面做出重大贡献。WAP水域中crenarchaeote表型的自然分离，加上其他人在同一地区进行的宏基因组研究（A. Murray， H. Ducklow），为了解这些生物的代谢能力提供了重大突破的可能性。这些知识是建立水柱硝化如何响应极地生态系统变化的模型所必需的。首席研究员将充分参与帕尔默LTER的教育和推广工作，包括将我们的研究成果的亮点发布到他们的项目网站上，并参与推广（例如，Schoolyard LTER）。该研究也将涉及本科生（包括实地工作，如果可能的话），并将支持高中实习生在P.I.这个夏天，他在他的实验室工作。

Ammonia oxidation is the first step in the conversion of regenerated nitrogen to dinitrogen gas, a 3-step pathway mediated by 3 distinct guilds of bacteria and archaea. Ammonia oxidation and the overall process of nitrification-denitrification have received relatively little attention in polar oceans where the effects of climate change on biogeochemical rates are likely to be pronounced. Previous work on Ammonia Oxidizing Archaea (AOA) in the Palmer LTER study area West of the Antarctic Peninsula (WAP), has suggested strong vertical segregation of crenarchaeote metabolism, with the "winter water" (WW, ~50-100 m depth range) dominated by non-AOA crenarchaeotes, while Crenarchaeota populations in the "circumpolar deep water" (CDW), which lies immediately below the winter water (150-3500 m), are dominated by AOA. Analysis of a limited number of samples from the Arctic Ocean did not reveal a comparable vertical segregation of AOA, and suggested that AOA and Crenarchaeota abundance is much lower there than in the Antarctic. These findings led to 3 hypotheses that will be tested in this project: 1) the apparent low abundance of Crenarchaeota and AOA in Arctic Ocean samples may be due to spatial or temporal variability in populations; 2) the WW population of Crenarchaeota in the WAP is dominated by a heterotroph; 3) the WW population of Crenarchaeota in the WAP "grows in" during spring and summer after this water mass forms. The study will contribute substantially to understanding an important aspect of the nitrogen cycle in the Palmer LTER (Long Term Ecological Research) study area by providing insights into the ecology and physiology of AOA. The natural segregation of crenarchaeote phenotypes in waters of the WAP, coupled with metagenomic studies in progress in the same area by others (A. Murray, H. Ducklow), offers the possibility of major breakthroughs in understanding of the metabolic capabilities of these organisms. This knowledge is needed to model how water column nitrification will respond to changes in polar ecosystems accompanying global climate change. The Principal Investigator will participate fully in the education and outreach efforts of the Palmer LTER, including making highlights of our findings available for posting to their project web site and participating in outreach (for example, Schoolyard LTER). The research also will involve undergraduates (including the field work if possible) and will support high school interns in the P.I.'s laboratory over the summer.