Collaborative Research: Geophysical Constraints on Sea- Ice Bacteria: Implications for Life on Ice-Covered Solar Bodies

该项目的总体目标是在相关的空间尺度上，更好地了解冬季海冰盐水孔隙中极低温下细菌活动的地球物理限制。固体表面作为细菌附着点的作用在假设的制定和检验中占有重要地位。主要有三个目标：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)确定冰基质内细菌的原位分布及其与不同表面的关系；3)在4至-300℃的温度下，检测盐水溶液中的细菌活性，作为溶解有机物浓度和不同表面存在的函数。该研究方法将北极海冰（已知携带矿物表面）的实地观测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。该计划依赖于评估细菌丰度和位置的标准方法（荧光和扫描电子显微镜）和选定的代谢活动（底物摄取和细胞外水解），但以新的方式应用（冰升华后，用于粘性零度以下的盐水）。还将采用对海冰进行物理和化学评估的标准方法，但要结合新技术（通过升华、核磁共振进行微尺度收集）。这一结果将大大扩展预测地球上微生物生命低温阈值的知识库，并可能在其他冰雪覆盖的太阳天体上进行预测。它们还应加强对极地微生物生态系统和海冰本身的季节性功能的理解，因为它影响全球热量收支和气候，以及低温细菌和酶在生物技术中的实际应用。

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.