Biogeochemical roles of planktonic archaea

古生菌，特别是克伦考古群，在几乎每个大洋盆地的深水微生物组合中占据主导地位，但人们对它们的生物地球化学作用知之甚少。最近，古生菌相关氨单加氧酶(Amo)基因的存在表明古生菌可能具有氨氧化能力，这是化学自养硝化作用的第一步。2005年培养的第一个非极端海洋考古考古菌证实了这一可能性，因为Maritimus亚硝化细菌能够在培养中氨氧化，并携带古生菌amoA基因。此外，这种基因似乎在海洋环境中广泛存在，这表明许多古菌都有氨氧化的能力。这个项目将通过实地观察和实验方法来评估这些新的见解。广泛地讲，它将讨论古细菌在海洋氨氧化中的作用，或在一般的氮和碳循环中的作用。更具体地说，它将检查是否所有或大多数新古生菌能够进行这种反应，以及它们在多大程度上也是异养或混合营养的，将在野外情况下测量古菌的氧化速率，并将检查古菌的种群动态。PI将把时间序列方法与分子技术和生物地球化学测量和实验结合起来。基本的假设是，有相当大比例的裸藻能够进行氨氧化，并在必要的底物可用时进行反应，但它们中的许多也能够利用溶解的有机物，因此是混合营养的。这项研究将在圣佩德罗海洋时间序列(Spot)站点进行，那里正在进行的一项独立资助的研究已经拥有5年的相关数据。到该项目完成时，7年以上的时间序列将与作为Spot的一部分收集的附带生物地球化学数据进行比较。该项目的更广泛影响包括博士后培训，通过南加州大学COSEE West项目与K-12教学的重要联系，本科教学和研究，以及包括一个网站的面向普通公众的推广。

Archaea, and specifically the Crenarchaeota, dominate microbial assemblages in deep waters throughout virtually every ocean basin, but little is known of their biogeochemical roles. Recently, the presence of an archaeal-associated ammonia monooxygenase (amo) gene indicated that archaea may be capable of ammonia oxidation, the first step of chemoautotrophic nitrification. Cultivation of the first non-extremophilic marine Crearchaeote in 2005 confirmed this possibility, as Nitrosopumilus maritimus is capable of ammonia oxidation in culture and carries an archaeal amoA gene. Moreover, this gene appears to be widespread in the marine environment, suggesting many archaea are capable of ammonia oxidation. This project will evaluate these new insights with field observations and experimental approaches. Broadly, it will address the role of archaea in marine ammonia oxidation, or in nitrogen and carbon cycling in general. More specifically, it will examine whether all or most Crenarchaeota capable of this reaction and to what extent they are also heterotrophic or mixotrophic, will measure archaeal oxidation rates in field situations, and will examine population dynamic of archaea. The PI will combine a time series approach with molecular techniques and biogeochemical measurements and experiments. The underlying hypothesis is that a significant proportion of Crenarchaeota are capable of ammonia oxidation and perform the reaction when necessary substrates are available, but that many of them are also capable of utilizing dissolved organic matter, and are therefore mixotrophic. The study will be at the San Pedro Ocean Time-series (SPOT) site, where an ongoing independently-funded study already has 5 years of relevant data. By the time the project is completed, a 7+ year time series will be compared with accompanying biogeochemical data that are collected as part of SPOT. Broader impacts of the project include postdoctoral training, a significant connection to K-12 teaching through USC's COSEE West program, undergraduate teaching and research, and outreach that will include a website with sections for the general public.