Dissertation Research: Do the concomitant effects of pH and ammonium concentration on ammonia availability explain differential ammonia oxidation by bacteria and archaea?

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Ammonia oxidation, a key step in the global nitrogen cycle, is only known to be performed by two groups of microorganisms, ammonia oxidizing bacteria and archaea. Although these groups both occur in large numbers in soil environments, they, like many microorganisms, may only be active under certain conditions. This study will investigate how environmental conditions interact to control the activity of ammonia oxidizing bacteria and archaea. Soil samples will be exposed to different environmental conditions and the activity of ammonia oxidizing bacteria and archaea will be measured using molecular based techniques. Experimental treatments will include variation in ammonium concentrations and soil pH, both of which have been shown to individually alter the activity of cultured representatives from these two groups. Use of naturally occurring populations of soil microorganisms will lend field relevance to these culture-based observations, and should lead to a better understanding of nitrification by investigating the ecology of the organisms that perform this important nutrient transformation in the nitrogen cycle.Broader impacts of this project will include an additional research opportunity for the doctoral student. In addition, undergraduate students will be involved in various aspects of this project, providing them with exposure to research and opportunities to develop their own independent research projects.