"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)." This project will evaluate the basic factors that allow ammonia oxidizing bacteria to respond to stress. An ecological framework based in differential gene expression at the community level will be integrated with deterministic mathematical models to accurately characterize the function of chemically stressed ammonia oxidizing bacteria and, if found to be relevant, ammonia oxidizing archaea. The operating hypothesis is that the resilience of ammonia oxidizers to stress is a function of microbial phylogenetic diversity in the stressed system and this resilience arises due to differences among strains in their investment of energy towards stress resistance at the expense of growth. The project uses whole cell physiological indicators and microbial ecology methods to follow the changes in the community diversity, species dominance, population-level activity, and differential gene expression of ammonia oxidizers perturbed with the heavy metals cadmium and copper. Laboratory-scale reactors containing bacterial communities will be maintained and exposed to copper and cadmium, and the behavior of the microorganisms in the bioreactors will be analyzed. This project will have broader impacts for systems where nitrification is often chemically stressed, including drinking water pipes that are disinfected with chloramines and aquaculture treatment systems where ammonia removal is key to optimum fish production. An increasing number of biotreatment systems are implementing nitrogen removal, as the water quality in many estuaries is deteriorating worldwide. Key to the nitrogen removal process is ammonia oxidation. Results from the experimental work will allow current computer models that are used to design wastewater treatment systems to be expanded and improved, thereby motivating the design of more robust nitrogen removal treatment systems. Finally, the participants in this program will integrate various project activities into an existing outreach program that develops environmental microbiology and engineering learning modules for grade school children to help them understand how microorganisms both harm and help humans.
