Dissertation Research: Microbial Population Dynamics and the Alpine Nitrogen Cycle

9801408蒙森通过对从土壤中分离的细菌和真菌进行实验，研究在科罗拉多高山冻原中观察到的微生物种群动态的机制。将使用斑点杂交技术筛选培养物收集物中在一年中的某个时候大量存在的分离物，该技术测量从土壤中提取的DNA样品中存在的分离物特异性DNA的量。这一过程将确定最生态相关的分离物，用于以后的实验。将使用脂肪酸分析和16S rRNA测序对这些微生物进行分类。环境限制（温度范围，底物利用模式，并耐冷冻和渗透胁迫）的特点为选定的分离株，这些数据将被用来测试假设的原因观察到的社区转变。季节性的社会转变是中央的高山N循环，因为在两个社区类型之间的过渡期，冬季微生物生物量释放一个大脉冲的N植物后不久，融雪。通过将观察到的整个土壤过程的模式与主要微生物的生理特性联系起来，这项工作将首次提供陆地氮循环的真正机械描述。

9801408 Monson The mechanisms responsible for the observed microbial population dynamics in the Colorado alpine tundra will be investigated by performing experiments on bacteria and fungi isolated from the soil. The culture collection will be screened for those isolates that are abundant at some part of the year using dot blot hybridization techniques, which measure the quantity of isolate-specific DNA that is present in a sample of DNA extracted from the soil. This process will identify the most ecologically relevant isolates for use in later experiments. These organisms will be classified using fatty acid analysis and 16S rRNA sequencing. The environmental limits (temperature range, substrate-utilization patterns, and resistance to freezing and osmotic stress) will be characterized for the selected isolates, and this data will be used to test hypotheses about the cause of the observed community shift. The seasonal community shift is central to the alpine N cycle because during the transitional period between the two community types, the winter microbial biomass releases a large pulse of N to plants shortly after snowmelt. By linking observed patterns of whole-soil processes to physiological properties of the dominant microorganisms, the work will provide the first truly mechanistic description of a terrestrial N cycle.