Bacteria in Glaciers: A Mechanism for Bacterial Speciation in an Extremely Cold Environment

近年来，冰川中细菌的存在引起了公众和科学界的极大兴趣。细菌从上方沉积在风吹的尘埃颗粒和气溶胶上，经过数千年的沉积和增生，最后通过冰川崩解和融化返回沿海海洋环境。 在几百年到几千年的冰川冰中发现并培养了细菌。 有证据表明，冰川冰不能支持细菌生长，而是将这些生物体困在合成代谢状态相当长的时间。 这项研究将测试细菌在冰川截留期间维持显著水平的DNA降解和损伤（碱基损伤）以及这种碱基损伤导致突变的假设。 将从国家冰芯实验室（NICL）获得代表广泛地理位置和年龄分布的冰芯样本。 目前和新兴的分子生物学工具将用于分析从这些冰芯中提取的细菌和细菌DNA。 从冰川冰中提取的各种细菌将被培养、保存和鉴定。 最近开发的技术，以检测和定量的单细菌细胞中的碱基丢失和脱氨基，使用损伤特异性核酸内切酶和可视化的双链断裂，使用微凝胶电泳。 将使用克隆性、转录、蛋白质合成和使用rRNA探针作为生物学终点的荧光杂交来检查冰川作用对细菌的致死作用。 还将通过比较16S rDNA基因保守和非保守区域内的序列同源性来估计细菌分离株中的相对突变频率。 从拟议的工作中，将深入了解诱变的基本机制，这些机制可能与地球上以及太阳系其他地方发现的极冷环境中的细菌物种形成，多样性和生命进化有关。

The presence of bacteria in glaciers has generated considerable public and scientific interest in recent times. Bacteria are deposited from above on wind-borne dust particles and aerosols, overlayered by thousands of years of deposition and accretion, and finally returned to the coastal marine environment by glacial calving and melting. Bacteria have been detected in and cultured from glacial ice ranging from a few hundred to many thousands of years old. Evidence suggests that glacial ice cannot support bacterial growth but rather traps these organisms for considerable lengths of time in an anabolic state. This research will test the hypothesis that bacteria sustain significant levels of DNA degradation and damage (base damage) during glacial entrapment and that this base damage leads to mutations. Ice core samples representing a wide range of geographical locales and age distributions will be obtained from the National Ice core Laboratory (NICL). Current and emerging molecular biology tools will be used to analyze bacteria and bacterial DNA extracted from these ice cores. A diverse array of bacteria extracted from glacial ice will be cultured, preserved, and characterized. A recently developed technology to detect and quantify base loss and deaminations in single bacterial cells using damage-specific endonucleases and visualization of double-strand breaks using microgel electrophoresis will be employed. The lethal effects of glaciation on bacteria using clonability, transcription, protein synthesis, and fluorescence hybridization using rRNA probes as biological endpoints will be examined. Relative mutation frequencies in bacterial isolates will also be estimated by comparing sequence homologies within conserved and nonconserved regions of the 16S rDNA genes. From the proposed work, insight will be gained into understanding basic mechanisms of mutagenesis that may be relevant to bacterial speciation, diversity and the evolution of life on earth as well as in extremely cold environments found elsewhere in our solar system.