title: Ammonia-oxidizing microbial communities in reactors with efficient nitrification at low-dissolved oxygen.
abstract: Ammonia-oxidizing microbial communities involved in ammonia oxidation under low dissolved oxygen (DO) conditions (<0.3 mg/L) were investigated using chemostat reactors. One lab-scale reactor (NS_LowDO) was seeded with sludge from a full-scale wastewater treatment plant (WWTP) not adapted to low-DO nitrification, while a second reactor (JP_LowDO) was seeded with sludge from a full-scale WWTP already achieving low-DO nitrifiaction. The experimental evidence from quantitative PCR, rDNA tag pyrosequencing, and fluorescence in situ hybridization (FISH) suggested that ammonia-oxidizing bacteria (AOB) in the Nitrosomonas genus were responsible for low-DO nitrification in the NS_LowDO reactor, whereas in the JP_LowDO reactor nitrification was not associated with any known ammonia-oxidizing prokaryote. Neither reactor had a significant population of ammonia-oxidizing archaea (AOA) or anaerobic ammonium oxidation (anammox) organisms. Organisms isolated from JP_LowDO were capable of autotrophic and heterotrophic ammonia utilization, albeit without stoichiometric accumulation of nitrite or nitrate. Based on the experimental evidence we propose that Pseudomonas, Xanthomonadaceae, Rhodococcus, and Sphingomonas are involved in nitrification under low-DO conditions.
authors.affiliation: Department of Civil and Environmental Engineering, University of Wisconsin - Madison, 1415 Engineering Drive, Madison, WI 53706, USA. Electronic address: colin.fitzgerald87@gmail.com.
authors.forename: Colin M
authors.initials: CM
authors.lastname: Fitzgerald
authors.affiliation: Department of Civil and Environmental Engineering, University of Wisconsin - Madison, 1415 Engineering Drive, Madison, WI 53706, USA. Electronic address: camejo.pamela@gmail.com.
authors.forename: Pamela
authors.initials: P
authors.lastname: Camejo
authors.affiliation: Department of Civil and Environmental Engineering, University of Wisconsin - Madison, 1415 Engineering Drive, Madison, WI 53706, USA. Electronic address: j.z.oshlag@gmail.com.
authors.forename: J Zachary
authors.initials: JZ
authors.lastname: Oshlag
authors.affiliation: Department of Civil and Environmental Engineering, University of Wisconsin - Madison, 1415 Engineering Drive, Madison, WI 53706, USA. Electronic address: noguera@engr.wisc.edu.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Noguera
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D001105:Archaea / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D019149:Bioreactors; D058465:Nitrification; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010802:Phylogeny; D012722:Sewage; D012995:Solubility
chemical_list: D012722:Sewage; D000641:Ammonia; D010100:Oxygen
keywords: Activated sludge; Ammonia oxidizing archaea; Ammonia oxidizing bacteria; Low dissolved oxygen; Nitrification