Microbe Hunters: Searching for Anammox Bacteria in the Tennessee Aquarium

Ammonium and nitrite are toxic metabolic waste products generated by aquatic macroorganisms. They are of particular concern in closed systems, such as commercial aquaria. Typically, biological filtration systems are employed to regulate levels of toxic N species as they are more cost-efficient compared to water removal and replacement. Microbial communities that reside in these systems play vital roles in transformation of toxic N species. Commonly, nitrite and ammonium are converted into nitrate via nitrification. However, even nitrate is toxic at higher concentrations. Bacteria belonging to the phylum Planctomycetes can transform ammonium and nitrite to N2 via anaerobic ammonium oxidation (anammox). In this study, we are investigating the presence and role of anammox bacteria in multiple tanks at the Tennessee Aquarium in Chattanooga, TN. DNA was extracted from water and filtration systems of four different aquaria. Metagenomic analyses, looking for the presence of genes diagnostic of the anammox reaction, were performed and no known annamox pathway-specific genes were identified. Given the typically low representation of Planctomycetes in microbial communities, a nested PCR approach targeting Planctomycete-specific16S rRNA genes was used to enrich for and identify organisms capable of anammox. Analysis using this targeted PCR approach is ongoing.