title: Candidatus Accumulibacter phosphatis clades enriched under cyclic anaerobic and microaerobic conditions simultaneously use different electron acceptors.
abstract: Lab- and pilot-scale simultaneous nitrification, denitrification and phosphorus removal-sequencing batch reactors were operated under cyclic anaerobic and micro-aerobic conditions. The use of oxygen, nitrite, and nitrate as electron acceptors by Candidatus Accumulibacter phosphatis during the micro-aerobic stage was investigated. A complete clade-level characterization of Accumulibacter in both reactors was performed using newly designed qPCR primers targeting the polyphosphate kinase gene (ppk1). In the lab-scale reactor, limited-oxygen conditions led to an alternated dominance of Clade IID and IC over the other clades. Results from batch tests when Clade IC was dominant (i.e., >92% of Accumulibacter) showed that this clade was capable of using oxygen, nitrite and nitrate as electron acceptors for P uptake. A more heterogeneous distribution of clades was found in the pilot-scale system (Clades IIA, IIB, IIC, IID, IA, and IC), and in this reactor, oxygen, nitrite and nitrate were also used as electron acceptors coupled to phosphorus uptake. However, nitrite was not an efficient electron acceptor in either reactor, and nitrate allowed only partial P removal. The results from the Clade IC dominated reactor indicated that either organisms in this clade can simultaneously use multiple electron acceptors under micro-aerobic conditions, or that the use of multiple electron acceptors by Clade IC is due to significant microdiversity within the Accumulibacter clades defined using the ppk1 gene.
authors.affiliation: Department of Civil and Environmental Engineering, University of Wisconsin - Madison, Madison, WI, USA. Electronic address: camejo.pamela@gmail.com.
authors.forename: Pamela Y
authors.initials: PY
authors.lastname: Camejo
authors.affiliation: Department of Civil and Environmental Engineering, University of Wisconsin - Madison, Madison, WI, USA. Electronic address: browen92@gmail.com.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Owen
authors.affiliation: Department of Civil and Environmental Engineering, University of Wisconsin - Madison, Madison, WI, USA. Electronic address: joemartirano@gmail.com.
authors.forename: Joseph
authors.initials: J
authors.lastname: Martirano
authors.affiliation: School of Environmental & Municipal Engineering, Lanzhou Jiaotong University, China. Electronic address: megymma@163.com.
authors.forename: Juan
authors.initials: J
authors.lastname: Ma
authors.affiliation: Environmental Protection Agency, Cincinnati, OH, USA. Electronic address: Kapoor.Vikram@epa.gov.
authors.forename: Vikram
authors.initials: V
authors.lastname: Kapoor
authors.affiliation: Environmental Protection Agency, Cincinnati, OH, USA. Electronic address: Santodomingo.Jorge@epa.gov.
authors.forename: Jorge
authors.initials: J
authors.lastname: Santo Domingo
authors.affiliation: Department of Civil and Environmental Engineering, University of Wisconsin - Madison, Madison, WI, USA; Department of Bacteriology, University of Wisconsin - Madison, Madison, WI, USA. Electronic address: trina.mcmahon@wisc.edu.
authors.forename: Katherine D
authors.initials: KD
authors.lastname: McMahon
authors.affiliation: Department of Civil and Environmental Engineering, University of Wisconsin - Madison, Madison, WI, USA. Electronic address: noguera@engr.wisc.edu.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Noguera
mesh_terms: D019149:Bioreactors; D058440:Denitrification; D004583:Electrons; D009573:Nitrites; D010758:Phosphorus; D012722:Sewage
chemical_list: D009573:Nitrites; D012722:Sewage; D010758:Phosphorus
keywords: Accumulibacter; DPAO; Low-DO nutrient removal; PAO; SNDPR; ppk1 gene