Dissertation Research: Microbial Population Dynamics and the Alpine Nitrogen Cycle

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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.