Physiology and ecology of ammonia-oxidizing Archaea

海洋泉古菌已被发现代表了海洋中浮游微生物群落的主要部分（高达40%）。丰富的海洋组1 Crenarchaeota，候选人Nitrosopumilus maritimus的第一个培养的成员，最近被分离到纯培养，首次显示硝化之间的域degenea。像已知的细菌氨氧化剂，N。maritmus将氨需氧转化为亚硝酸盐并固定无机碳用于生物合成。这个建议的第一个目的是了解唯一存在的纯培养物的化能无机自养生命所涉及的生化途径。这些研究将与华盛顿大学的大卫斯塔尔密切合作，并由联合基因组研究所正在进行的全基因组分析促进。我们的部分将是参与碳代谢的酶的生物化学和微生物分析以及假设途径的批准。将进行示踪实验以确定N。海洋生物是严格的自养生物或混合营养生物。N生长过程中碳同位素分馏的测定。maritimus将提供关于碳固定途径的信息。从环境基因组学的泉古菌海绵共生体的CO2固定的修改3-羟基丙酸循环的存在将被证明在N。maritimus拟议项目的第二个目标是分析预测的高丰度和多样性的泉古菌氨氧化剂在自然环境中。以前的16 S rRNA和amoA基因的分析表明，这组的普遍分布。然而，目前尚不清楚其成员是否在体内氧化氨。这两个基因的系统发育多样性表明存在各种生理型。在我们的项目中，我们将从已经检测到相应生物标志物的水生和陆地环境中分离出更多菌株。新菌株将进行生理学表征，并将有助于理解对地球化学氮和碳循环的高影响。

Marine Crenarchaeota have been found to represent a major fraction (up to 40 %) of the planktonic microbial community in the Ocean. The first cultured member of the abundant marine group 1 Crenarchaeota, candidatus Nitrosopumilus maritimus, was recently isolated into pure culture, showing for the first time nitrification among the domain Archaea. Like known bacterial ammonia oxidizers, N. maritmus converts aerobically ammonia to nitrite and fixes inorganic carbon for biosynthesis. The first aim of this proposal is to understand the biochemical pathways involved in the chemolithoautotrophic life of the only existing pure culture. The studies will be performed in close collaboration with David Stahl at the University of Washington and facilitated by the ongoing whole genome analysis at the Joint Genome Institute. Our part will be the biochemical and microbiological analysis of enzymes involved in the carbon metabolism and the approval of hypothetical pathways. Tracer experiments will be performed to determine if N. maritimus is either strict autotroph or mixotroph. Determination of the carbon isotope fractionation during growth of N. maritimus will provide information on the carbon fixation pathway. The existence of a modified 3-hydroxypropionate cycle for CO2 fixation derived from environmental genomics of crenarchaeal sponge symbionts will be proven biochemically in N. maritimus. The second goal of the proposed project is to analyze the predicted high abundance and diversity of crenarchaeal ammonia oxidizers in natural environments. Previous analyses of 16S rRNA and amoA genes have indicated a ubiquitous distribution of this group. However, it is unclear whether its members are oxidizing ammonia in vivo. The phylogenetic diversity of both genes suggests the existence of various physiotypes. In our project we will isolate further strains from aquatic and terrestrial environments where the corresponding biomarkers have been detected. The new strains will be characterized physiologically and will help to understand the suggested high impact on the biogeochemical nitrogen and carbon cycles.