Unraveling the black box of aquaria biofilter function: FISHing for novel ammonia-oxidizing archaea associations

Nitrification, a biological link between the oxidized and reduced pools of inorganic nitrogen is typically limited by the first step, ammonia oxidation. Often controlled by ammonia oxidizing archaea (AOA), nitrification involves archaea within Thaumarcheota as well as bacteria from Gammaproteobacteria and Betaproteobacteria. This study examines how AOA associate with the ammonia oxidizing bacteria, and the specific spatial interaction between AOA/AOB and nitrite oxidizing bacteria through microscopy. Water and biofilm samples were collected from three seawater fish tanks and throughout the aquaria at the Marine Resources Center (MRC), Marine Biological Laboratory, Woods’ Hole, MA to determine if nutrient availability or temperature affect these microbial assemblages through Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) and confocal laser scanning microscopy. Within the closed loop aquaria, the microbial consortia present were significantly different at different points throughout the system due to the local nutrient and temperature conditions.