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

氨氧化是将再生氮气转化为氮气的第一步，这是一个由3个不同的细菌和古细菌协会介导的3步途径。在极地海洋中，氨氧化和整个硝化-反硝化过程受到的关注相对较少，因为气候变化对生物地球化学速率的影响可能很大。前人对南极半岛西部Palmer LTER研究区氨氧化古生物(AOA)的研究表明，古考古动物代谢在垂直方向上存在很强的分离，“冬水”(WW，~50-100m深度范围)以非AOA古生物为主，而位于冬季水(150-3500 m)正下方的“环极深水”(CDW)中的Cren考古动物群则以AOA为主。对数量有限的北冰洋样品的分析没有显示出类似的AOA的垂直分离，并表明那里的AOA和Crenaceota的丰度比南极低得多。这些发现导致了将在本项目中检验的3个假说：1)北冰洋样本中Crenarocota和AOA的明显低丰度可能是由于种群的空间或时间变异性；2)WAP中Crenaceota的WW种群由异养体主导；3)WW种群在WAP的Crenaceota种群在该水团形成后的春季和夏季“增长”。这项研究将有助于理解Palmer LTER(长期生态研究)研究区域氮循环的一个重要方面，因为它提供了对AOA的生态学和生理学的见解。WAP水域中考古菌表型的自然分离，加上其他人(A.Murray，H.Ducklow)在同一领域正在进行的元基因组研究，为理解这些生物的代谢能力提供了重大突破的可能性。需要这种知识来模拟水柱硝化作用将如何应对伴随全球气候变化的极地生态系统的变化。首席调查员将全面参与Palmer LTER的教育和外联工作，包括将我们的调查结果重点张贴在他们的项目网站上，并参与外联(例如，School Oard LTER)。这项研究还将包括本科生(如果可能的话，还包括实地考察)，并将在暑期为P.I.S实验室的高中实习生提供支持。

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.