Niche differentiation between Ammonia-oxidizing Archaea and Bacteria in Freshwater lakes

Miami University, Oxford OH

Investigators

Abstract

The nitrogen cycle is one of the most important nutrient cycles on the planet. Nitrification, the biological conversion of ammonium to nitrate, occurs in almost all environments, including soils, sediments, fresh and marine waters and wastewater, and can cause serious environmental problems such as promotion of algal blooms and subsequent creation of dead zones in aquatic systems. This research project concerns the first and rate limiting step of nitrification, the oxidation of ammonia to nitrite. Ammonia-oxidizing bacteria have been studied for over 100 years, and until recently scientists assumed that they were the sole microbes responsible for ammonia oxidation in the environment. However, a new player in the oxidation of ammonia to nitrite was discovered very recently, the ammonia-oxidizing Archaea. Both groups use the same resources due to the similarity in their basic energy generating metabolism, and are found in a wide variety of environments together. This project will address the question of which group of ammonia-oxidizing microbes is responsible for ammonia oxidation in different habitats. The project focuses on open water and bottom sediment habitats in Lake Acton, a freshwater lake in Ohio, and will test the hypothesis that these two groups of ammonium oxidizing microbes display niche differentiation. The experimental efforts will focus on cultivation dependent approaches to investigate the response of ammonia-oxidizing microbes to environmental factors under controlled conditions in the laboratory. In addition, a novel culture transplant experiment will be used to link the response of the Archaea and bacteria to natural conditions in the lake. This project will contribute more broadly to strengthen interdisciplinary research in microbial ecology through the collaboration of two early career scientists. Graduate and undergraduate students will be engaged in active research on the project and participate in a genome annotation project. In addition, a one-week class will be developed and offered at Miami University to educate K-12 teachers about water quality with a focus on wastewater treatment and water purification.