ABSTRACT
Ammonia-oxidizing archaea (AOA) have recently been proposed as potential players for ammonia removal in wastewater treatment plants (WWTPs). However, there is little evidence directly showing the contribution of AOA to ammonia oxidation in these engineered systems. In this study, DNA-stable isotope probing (DNA-SIP) with labeled 13C-HCO3- was introduced to sludge from a municipal WWTP. Quantitative PCR demonstrated that AOA amoA genes outnumbered AOB amoA genes in this WWTP sludge. AOA amoA gene sequence analysis revealed that AOA present in this WWTP were specific to one subcluster within the group 1.1b Thaumarchaeota. When ammonia was supplied to DNA-SIP incubation, the DNA-SIP profiles demonstrated the incorporation of the 13C into AOA and AOB. However, the 13C was not found to be assimilated into both microorganisms in the incubation without ammonia. Specific primers were designed to target amoA genes of AOA belonging to the subcluster found in this WWTP. Applying the primers to DNA-SIP experiment revealed that AOA of this subcluter most likely utilized inorganic carbon during ammonia oxidation under the studied conditions.
Subject(s)
Ammonia/metabolism , Archaea/metabolism , Bacteria/metabolism , Carbon Isotopes/metabolism , Waste Disposal, Fluid/methods , Archaea/genetics , Bacteria/genetics , Bicarbonates/metabolism , DNA Primers , Oxidation-Reduction , Phylogeny , Polymerase Chain Reaction , Sewage , ThailandABSTRACT
In this study, two laboratory nitrifying reactors (NRI and NRII), which were seeded by sludge from different sources and operated under different operating conditions, were found to possess distinct dominant ammonia-oxidizing microorganisms. Ammonia-oxidizing archaeal (AOA) amoA genes outnumbered ammonia-oxidizing bacterial (AOB) amoA genes in reactor NRI, while only AOB amoA genes were detectable in reactor NRII. The AOA amoA gene sequences retrieved from NRI were characterized within the Nitrososphaera sister cluster of the group 1.1b Thaumarchaeota. Two inhibitors for ammonia oxidation, allylthiourea (ATU) and 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO), were applied individually and as a mixture to observe the ammonia-oxidizing activity of both microorganisms in the reactors' sludge. The results indicated that AOA and AOB jointly oxidized ammonia in NRI, while AOB played the main role in ammonia oxidation in NRII. DNA-stable isotope probing with labeled 13C-HCO3- was performed on NRI sludge. Incorporation of 13C into AOA and AOB implied that both microorganisms may perform autotrophy during ammonia oxidation. Taken together, the results from this study provide direct evidence demonstrating the contribution of AOA and AOB to ammonia oxidation in the nitrifying reactors.
Subject(s)
Ammonia/analysis , Archaea/isolation & purification , Betaproteobacteria/isolation & purification , Bioreactors/microbiology , Water Pollutants, Chemical/analysis , Water Purification/methods , Archaea/genetics , Autotrophic Processes , Betaproteobacteria/genetics , Oxidation-Reduction , Phylogeny , Sewage/microbiologyABSTRACT
Recent evidence from natural environments suggests that in addition to ammonia-oxidizing bacteria, ammonia-oxidizing archaea (AOA) affiliated with Thaumarcheota, a new phylum of the domain Archaea, also oxidize ammonia to nitrite and thus participate in the global nitrogen cycle. Besides natural environments, modern data indicate the presence of amoA-encoding archaea (AEA) in wastewater treatment plants (WWTPs). To further elucidate whether AEA in WWTPs are AOA and to clarify the role of AEA in WWTPs, this paper reviews the current knowledge on this matter for wastewater engineers and people in related fields. The initial section coveys a microbiological point of view and is particularly based upon data from AOA cultures. The later section summarizes what is currently known about AEA in relation to WWTPs. Based on the reviewed data, future research pathways are proposed in an effort to further what is known about AEA in wastewater treatment systems.
