LEXEN: A Collaborative Proposal on Geophysical Constraints on Sea-Ice Bacteria: Implications for Life on Ice-Covered Solar Bodies

该项目的总体目标是更好地了解在相关的空间尺度上，冬季海冰盐水孔中极低温度下细菌活动的地球物理约束。固体表面作为细菌附着位点的作用在假说的形成和检验中具有重要意义。三个主要目标是：1）在与微生物相关的尺度上表征海冰孔隙中不同相组分的演化和空间分布; 2）确定冰基质中细菌的原位分布及其与不同表面的关联;和3）在4 - 10 ℃的温度下检查盐水溶液中的细菌活性。300 C作为溶解的有机物的浓度和不同表面的存在的函数。该研究方法将北极海冰（已知夹带矿物表面）的实地观察与新的实验室实验相结合，旨在描述海冰在温度下降时演变的微观物理特征，并测量微生物对日益极端的热和化学条件的反应。该计划依赖于用于评估细菌丰度和位置（落射荧光和扫描电子显微镜）以及选定的代谢活动（底物摄取和细胞外水解）的标准方法，但以新的方式应用（冰升华后，粘性零度以下的盐水）。还将采用海冰物理和化学评估的标准方法，但要结合新技术（升华法、核磁共振法的微型收集）。研究结果将大大扩大知识基础，以预测地球上微生物生命的低温阈值，并可能在其他地方的冰层覆盖的太阳能机构。它们还应增进对极地微生物生态系统和海冰本身的季节性功能的了解，因为它影响全球热量收支和气候，并增进对低温细菌和酶在生物技术中的实际应用的了解。

ABSTRACTDeming, JodyEicken, HajoThe overall goal of the project is to better understand, at relevant spatial scales, the geophysical constraints on bacterial activity at very low temperatures in the brine pores of wintertime sea ice. The role of solid surfaces as attachment sites for bacteria figures strongly in the formulation and testing of hypotheses. The three main objectives are: 1) to characterize the evolution and spatial distribution of the different phase components in sea-ice pores on scales relevant to microorganisms; 2) to determine the in-situ distribution of bacteria within the ice matrix and their association with different surfaces; and 3) to examine bacterial activity in brine solutions at temperatures from 4 to -300C as a function of concentration of dissolved organic matter and presence of different surfaces. The research approach combines field observations of Arctic sea ice (known to entrain mineral surfaces) with novel laboratory experiments designed to characterize micro-physical features of sea-ice as it evolves at decreasing temperature and to measure microbial reactions to increasingly extreme thermal and chemical conditions. The plan relies upon standard methods for assessing bacterial abundance and location (epifluorescence and scanning electron microscopy) and selected metabolic activities (substrate uptake and extracellular hydrolysis), but applied in new ways (after ice sublimation, to viscous sub-zero brines). Standard methods for physical and chemical assessments of sea ice will also be employed, but in combination with novel techniques (micro-scale collections by sublimation, NMR). Results will significantly expand the knowledge base for predicting the lower temperature threshold for microbial life on Earth and possibly elsewhere on ice-covered solar bodies. They should also enhance understanding of the seasonal functioning of polar microbial ecosystems and sea-ice itself, as it effects the global heat budget and climate, and practical applications of low-temperature bacteria and enzymes in biotechnology.