Microbial Activity in Solid Ice: Implications for Modifying the CO2 Record in Ice Cores

固体冰中的微生物活动：对修改冰芯中二氧化碳记录的影响最近对古冰川冰中微生物寿命的研究表明，细菌在冷冻状态下仍能存活数十万年。在缺乏代谢活性的情况下，大分子损伤必须通过氨基酸消旋、DNA去嘌呤化和暴露于自然电离辐射（例如40K）而积累。也许恢复的物种在长时间的代谢休眠中特别成功，但也有可能这些被困的微生物可能会进行缓慢的代谢来修复发生的大分子损伤。拟议的研究将检验从冰川环境中分离出来的细菌代谢和呼吸人工构建的冰基质液体部分中的二氧化碳的能力。将进行实验，以检查在冷冻条件下温度和未冻水化学对微生物活动的影响。此外，我们还将通过定量活细胞和呼吸细胞的比例以及表征在冷冻条件下表达的基因和蛋白质来研究冰包埋细胞的生理学。重要的是，提出的研究代表了在环境条件下（-5至-20℃）测量微生物CO2呼吸和大分子合成的第一次尝试，在这种条件下，据报道冰川冰芯和来自冷基冰川的基冰中CO2浓度升高。拟议研究的结果与微生物在永久冰冻环境中可能保持代谢活性的观点有关，因此支持冰盖是一个活跃的生物群系的观点。这些信息对冰芯群落尤其重要，因为冰川冰内的微生物活动会歪曲基于冰中气泡气体成分的古气候推断。我们的研究结果也将潜在地为鉴定具有改进冷活性特性的酶提供生物技术相关信息。这些数据将对有关微生物在火星或木卫二冰中的持久性和生存的天体生物学讨论产生影响。该提案将支持2名新的研究人员，并为1名博士生和2名本科生提供培训。PI和CoI目前作为导师参与蒙大拿州立大学的美国印第安人研究机会（AIRO）项目，该项目的2名高中生将参与本研究过程中的研究项目。通过将我们的研究结果纳入蒙大拿州立大学正在建设的国家科学基金会资助的（DERMEED-1）图书馆，作为国家（SMETE）数字图书馆的一部分，针对有兴趣从事科学事业的学生的基于网络的工具将得到维护和扩展。

EAR-0525567Microbial Activity in Solid Ice: Implications for Modifying the CO2 Record in Ice Cores Recent studies of microbial longevity in ancient glacial ice indicate that bacteria remain viable for hundreds of thousands of years while frozen. In the absence of metabolic activity, macromolecular damage must accumulate through amino acid racemization, DNA depurination, and exposure to natural ionizing radiation (e.g., 40K). Perhaps the species recovered are particularly successful at surviving metabolic dormancy over extended time frames, but it is also possible that such entrapped microbes might carry out a slow rate of metabolism to repair incurred macromolecular damage. The proposed study will examine the ability of bacteria isolated from glaciated environments to metabolize and respire CO2 in the liquid fraction of artificially constructed ice matrices. Experiments will be undertaken to examine the influence of temperature and unfrozen water chemistry on microbial activity under frozen conditions. In addition, we will also study the physiology of cells entrapped in ice by quantifying the fraction of viable and respiring cells and characterizing the genes and proteins expressed under frozen conditions. Importantly, the proposed research represents the first attempt to measure microbial CO2 respiration and macromolecular synthesis under environmental conditions (-5 to -20oC) in which elevated CO2 concentrations have been reported in glacial ice cores and basal ice from cold based glaciers.Results from the proposed study are relevant to the notion that microorganisms in permanently frozen environments may remain metabolically active, thus supporting the view that ice sheets are an active biome. Such information is especially vital to the ice core community, as microbial activity within glacial ice would skew paleoclimatic inferences based on gas composition of bubbles in the ice. Our results will also potentially yield biotechnologically relevant information for the identification of enzymes with improved cold-active properties. These data will have implications relevant to astrobiological discussions about microbial persistence and survival in ice on Mars or Europa. This proposal would support 2 new investigators, and provide training for a Ph.D. student, and 2 undergraduate students. The PI and CoI currently participate as mentors in the American Indian Research Opportunities (AIRO) program at Montana State University, and 2 high school students from this program will be involved in research projects during the course of this study. Web-based tools to target students interested in pursuing a career in science will be maintained and expanded upon by incorporating our results into the NSF funded (DERMEED-1) library under construction at Montana State University, as part of the national (SMETE) digital library.