Exploring nitrification within engineered aquatic environments

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Treatment of municipal wastewater involves microorganisms (bacteria and archaea) using the components of waste as energy sources and, in the process, reducing the toxicity of effluent for fish and other wildlife in the rivers and lakes that receive this treated water. Understanding the microbial populations and processes involved in the process of nitrification (use of ammonia and nitrite as energy sources while breathing oxygen) is essential for optimizing water treatment processes and infrastructure design. Although ammonia-oxidizing bacteria and nitrite-oxidizing bacteria were regarded as sole contributors to nitrification for over a century, the discovery of both ammonia-oxidizing archaea and Nitrospira bacteria capable of complete ammonia oxidation (comammox) greatly expands knowledge of nitrification within aquatic, terrestrial, and engineered environments. My research team will use engineered water treatment systems, such as aquarium filters and rotating biological contactors in Guelph, Ontario, to compare populations, diversity, functions, and interactions of nitrifiers, with a particular emphasis on the newly discovered archaea and comammox bacteria involved in ammonia oxidation. We will also characterize the physiology and metabolism of the archaea we cultivated recently, with a focus on identifying their affinity for ammonia and ability to assimilate organic carbon sources. We will also test the hypothesis that these ammonia-oxidizing archaea can outcompete more traditional ammonia oxidizers because they can take advantage of organic carbon substrates that their bacterial counterparts cannot use. We will also apply cutting-edge microscopic approaches to visualize the spatial distributions of these contributors to nitrification within biofilm itself, which will help us better understand interactions of these unique groups that superficially appear to be responsible for the same processes. Because the archaea found in the wastewater biofilms are also found on human skin, we will explore the microorganisms on mammalian skin samples taken from multiple species and body sites to help identify the natural habitat of these archaea and investigate their potential interactions with host health. Together, my basic research program will shed new light on the genes, cells, and molecules that are relevant to nitrogen cycling with engineered water treatment systems, which serve as powerful microcosms of these same processes as they occur in myriad aquatic, terrestrial, and host-associated environments on a global scale.