Anaerobic ammonium oxidation discovered in a denitrifying fluidized bed reactor

The Athabasca oil sand deposit is one of the largest single oil deposits in the world. Following surface mining, companies are required to restore soil-like profiles that can support the previous land capabilities. The objective of this study was to assess whether the soil prokaryotic alpha diversity (␣-diversity) and ␤-diversity in oil sand soils reconstructed 20 to 30 years previously and planted to one of three vegetation types (coniferous or deciduous trees and grassland) were similar to those found in natural boreal forest soils subject to wildfire disturbance. Prokaryotic ␣-diversity and ␤-diversity were assessed using massively parallel sequencing of 16S rRNA genes. The ␤-diversity, but not the ␣-diversity, differed between reconstructed and natural soils. Bacteria associated with an oligotrophic lifestyle were more abundant in natural forest soils, whereas bacteria associated with a copiotrophic lifestyle were more abundant in reconstructed soils. Ammonia-oxidizing archaea were most abundant in reconstructed soils planted with grasses. Plant species were the main factor influencing ␣-diversity in natural and in reconstructed soils. Nitrogen deposition, pH, and plant species were the main factors influencing the ␤-diversity of the prokaryotic communities in natural and reconstructed soils. The results highlight the importance of nitrogen deposition and aboveground-belowground relationships in shaping soil microbial communities in natural and reconstructed soils. IMPORTANCE Covering over 800 km 2 , land disturbed by the exploitation of the oil sands in Canada has to be restored. Here, we take advantage of the proximity between these reconstructed ecosystems and the boreal forest surrounding the oil sand mining area to study soil microbial community structure and processes in both natural and nonnatural environments. By identifying key characteristics shaping the structure of soil microbial communities, this study improved our understanding of how vegetation, soil characteristics and microbial communities interact and drive soil functions.KEYWORDS biodiversity, boreal forest soil, microbial community, nitrogen deposition, oil sands, plant community, soil restoration, soil microbiology T he Athabasca oil sand deposit, located in the boreal forests of northern Alberta, is part of the largest single oil deposit in the world, with proven reserves of 166 billion barrels of bitumen and covering 142,200 km 2 (1). Most of the bituminous sands (80%) can be extracted using in situ recovery methods (i.e., steam injection wells), but 20% of

Section: Discussionmentioning

confidence: 99%

Plant Community and Nitrogen Deposition as Drivers of Alpha and Beta Diversities of Prokaryotes in Reconstructed Oil Sand Soils and Natural Boreal Forest Soils

Masse

Prescott

Renaut

et al. 2017

“…icrobially mediated anaerobic ammonium oxidation (anammox), which was predicted by Broda (1) on the basis of thermodynamic calculations, was first confirmed in the 1990s in a denitrifying pilot plant (2). Thermodynamically, it was believed that microorganisms capable of using nitrite as an electron acceptor for anaerobic methane oxidation could also exist in nature (3).…”

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confidence: 99%

Evidence for the Cooccurrence of Nitrite-Dependent Anaerobic Ammonium and Methane Oxidation Processes in a Flooded Paddy Field

Shen

Liu

Huang

et al. 2014

113

Anaerobic ammonium oxidation (anammox) and nitrite-dependent anaerobic methane oxidation (n-damo) are two of the most recent discoveries in the microbial nitrogen cycle. In the present study, we provide direct evidence for the cooccurrence of the anammox and n-damo processes in a flooded paddy field in southeastern China. Stable isotope experiments showed that the potential anammox rates ranged from 5.6 to 22.7 nmol N 2 g ؊1 (dry weight) day ؊1 and the potential n-damo rates varied from 0.2 to 2.1 nmol CO 2 g ؊1 (dry weight) day ؊1 in different layers of soil cores. Quantitative PCR showed that the abundance of anammox bacteria ranged from 1.0 ؋ 10 5 to 2.0 ؋ 10 6 copies g ؊1 (dry weight) in different layers of soil cores and the abundance of n-damo bacteria varied from 3.8 ؋ 10 5 to 6.1 ؋ 10 6 copies g ؊1 (dry weight). Phylogenetic analyses of the recovered 16S rRNA gene sequences showed that anammox bacteria affiliated with "Candidatus Brocadia" and "Candidatus Kuenenia" and n-damo bacteria related to "Candidatus Methylomirabilis oxyfera" were present in the soil cores. It is estimated that a total loss of 50.7 g N m ؊2 per year could be linked to the anammox process, which is at intermediate levels for the nitrogen flux ranges of aerobic ammonium oxidation and denitrification reported in wetland soils. In addition, it is estimated that a total of 0.14 g CH 4 m ؊2 per year could be oxidized via the n-damo process, while this rate is at the lower end of the aerobic methane oxidation rates reported in wetland soils.

“…In oxygen-minimum zones it was first hypothesized that sulfur cycling was linked to anammox via sulfide-driven DNRA (15). Anammox microorganisms were originally found in a sulfidic wastewater treatment bed (16), and DNRA has been demonstrated to support anammox organisms in an enrichment culture where sulfide was used as the electron acceptor for nitrate reduction (17). At high enough concentrations, sulfide can promote DNRA by diverting nitrogen away from the canonical denitrification pathway due to inhibition of NO Ϫ and N 2 O Ϫ reductases (18) as well as by inhibiting nitrification (19).…”

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confidence: 99%

Sulfide-Induced Dissimilatory Nitrate Reduction to Ammonium Supports Anaerobic Ammonium Oxidation (Anammox) in an Open-Water Unit Process Wetland

Jones

Jasper

Sedlak

et al. 2017

Open-water unit process wetlands host a benthic diatomaceous and bacterial assemblage capable of nitrate removal from treated municipal wastewater with unexpected contributions from anammox processes. In exploring mechanistic drivers of anammox, 16S rRNA gene sequencing profiles of the biomat revealed significant microbial community shifts along the flow path and with depth. Notably, there was an increasing abundance of sulfate reducers (Desulfococcus and other Deltaproteobacteria) and anammox microorganisms (Brocadiaceae) with depth. Pore water profiles demonstrated that nitrate and sulfate concentrations exhibited a commensurate decrease with biomat depth accompanied by the accumulation of ammonium. Quantitative PCR targeting the anammox hydrazine synthase gene, hzsA, revealed a 3-fold increase in abundance with biomat depth as well as a 2-fold increase in the sulfate reductase gene, dsrA. These microbial and geochemical trends were most pronounced in proximity to the influent region of the wetland where the biomat was thickest and influent nitrate concentrations were highest. While direct genetic queries for dissimilatory nitrate reduction to ammonium (DNRA) microorganisms proved unsuccessful, an increasing depth-dependent dominance of Gammaproteobacteria and diatoms that have previously been functionally linked to DNRA was observed. To further explore this potential, a series of microcosms containing field-derived biomat material confirmed the ability of the community to produce sulfide and reduce nitrate; however, significant ammonium production was observed only in the presence of hydrogen sulfide. Collectively, these results suggest that biogenic sulfide induces DNRA, which in turn can explain the requisite coproduction of ammonium and nitrite from nitrified effluent necessary to sustain the anammox community.IMPORTANCE This study aims to increase understanding of why and how anammox is occurring in an engineered wetland with limited exogenous contributions of ammonium and nitrite. In doing so, the study has implications for how geochemical parameters could potentially be leveraged to impact nutrient cycling and attenuation during the operation of treatment wetlands. The work also contributes to ongoing discussions about biogeochemical signatures surrounding anammox processes and enhances our understanding of the contributions of anammox processes in freshwater environments.KEYWORDS DNRA, anammox, nitrogen cycle, sulfide, water treatment, wetlands C onstructed freshwater wetlands that receive wastewater effluent offer an opportunity to gain insight into the biological nutrient cycling process because they are subject to comparatively high nutrient loading rates and are optimized for steady-state