Dissertation Research: Microbial Population Dynamics and the Alpine Nitrogen Cycle

9801408蒙森将通过对从土壤中分离出的细菌和真菌进行实验，来研究在科罗拉多州高山冻土带观察到的微生物种群动态的机制。培养物收集将使用斑点杂交技术来筛选那些在一年中的某个时间大量存在的菌株，这种技术测量从土壤中提取的DNA样本中存在的特定于菌株的DNA的数量。这一过程将确定最具生态相关性的菌株，供以后的实验使用。这些生物将使用脂肪酸分析和16S rRNA测序进行分类。环境极限(温度范围，底物利用模式，以及对冰冻和渗透胁迫的抵抗力)将被表征，这些数据将被用来检验关于所观察到的群落转移原因的假设。季节群落转移是高山N循环的中心，因为在两种群落类型之间的过渡期，冬季微生物生物量在融雪后不久向植物释放大量N脉冲。通过将观察到的全土壤过程模式与优势微生物的生理特性联系起来，这项工作将首次提供对陆地氮循环的真正机械性描述。

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.