Antarctic Lake Ice Microbial Consortia: Origin, Distribution and Growth Physiology

麦克默多干谷内南极湖泊的永久冰层为蓝藻和真细菌组成的微生物群落提供了栖息地。这种微生物组合集中在与冰中深度的一层岩石碎屑相关联的液态水透镜中，可能只在冰盖未完全冻结的时期（190 d- 1）生长。尽管这一组合可能对整个生态系统动力学具有潜在的重要性，但从未对其起源、分布和生态意义进行过研究。假设：(1)所有干谷湖的冰盖中都存在有活力的微生物群落；(2)微生物起源于陆生席群落；(3)由于太阳能量吸收和表面消融和底部冰冻结的向上平流之间的平衡，岩石碎屑和相关微生物层在冰中深度持续存在；(4)冰蓝藻的初级生产为湖泊生态系统贡献了大量的新产品。(5)微生物生长速率较低，但高于冰周转率；(6)与微生物组合相关的氮池是由N2固定产生的；(7)组合内的细菌和蓝藻相互作用是共生的。这些假设将通过地理采样、物理冰模型、使用16S rRNA和氮酶探针进行分子鉴定以及生理分析来解决。这项工作的大部分将集中在邦尼湖东叶发现的组合上，该组合已初步表征。这个项目将是第一个研究南极湖冰微生物组合的项目，它将产生关于麦克默多干谷中碳和氮动态的重要新信息，并将补充许多关于海冰微生物群落的研究。

9419413 Priscu The permanent ice cover of antarctic lakes within the McMurdo dry valleys provides a habitat for viable microbial consortia consisting of cyanobacteria and eubacteria. This microbial assemblage, which is concentrated in a liquid water lens associate with a layer of rock debris at mid-ice depth, presumably grows only during a period when the ice cover in not completely frozen ( 190 d y-1). Despite the potential importance this assemblage may have with regards to overall ecosystem dynamics, it has never been studied with respect to its origin, distribution and ecological significance. It is hypothesized that (1) viable microbial consortia exist in the ice covers of all dry valley lakes, (2) the microorganisms originate from terrestrial mat communities, (3) the rock debris and associated microbial layer persists at mid-ice depths owing to a balance between solar energy absorption and upward advection from surface ablation and bottom ice freezing, (4) primary production by ice cyanobacteria contributes a significant amount of new production to the lake ecosystem, (5) microbial growth rates are low but are higher than rates of ice turnover, (6) the nitrogen pool associated with the microbial assemblage results from N2 fixation and (7) bacterial and cyanobacterial interactions within the assemblage are commensualistic. These hypotheses will be addressed through a combination of geographical sampling, physical ice modeling, molecular identification using probes for 16S rRNA and nitrogenase, and physiological assays. A majority of this work will focus on the assemblage found in the east lobe of Lake Bonney which has been tentatively characterized. This project, which will be the first to examine the antarctic lake ice microbial assemblage, will yield important new information on carbon and nitrogen dynamics within the McMurdo dry valleys and will complement numerous studies of sea ice microbial communities.