A laboratory-scale anaerobic ammonium oxidation (anammox) bioreactor community followed from inoculation through a performance destabilization event and back to robust steady-state operation, characterized by metagenomics. Metabolic analyses showed selection for nutrient-acquisition capacities in the core community. Dissimilatory nitrate reduction to ammonium (DNRA) was the primary nitrogen-removal pathway that competed with anammox, and increased replication of DNRA-capable bacteria out-competed anammox bacteria, causing the loss of nitrogen-removal capacity. The DNRA-capable bacteria were closely associated with the anammox bacterium and are considered part of the core microbial community, underscoring how bacteria that are otherwise core members can be detrimental.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| anammox bacterium — ontology label: Planctomycetota | NCBITaxon:203682 · TaxonMech · TraitMech | DOMINANT | |
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| dissimilatory nitrate reducing (DNRA) bacteria — ontology label: Bacteria | NCBITaxon:2 · TaxonMech · TraitMech | N/A | |
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Ecological Interactions
The graph shows only explicitly linked interaction participants. Community members without an asserted participant link are omitted; membership alone does not imply an interaction.
Nutrient-Acquisition Core Selection
Genome comparisons showed enrichment of nutrient-acquisition transporters in the mature anammox-associated core relative to source-associated genomes. This supports inferred selection for acquisition potential, not a demonstrated complementary niche-partitioning mechanism.
Biological Processes:
- biological process involved in interspecies interaction between organisms (GO:0044419 · PathwayMech)
Evidence
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PMID:31980038 - SUPPORT (COMPUTATIONAL)"nutrient acquisition from the environment is selected for in the anammox community "
Brocadia Ammonium-Nitrite Anammox
The reactor removed nitrogen through anammox, and the recovered Brocadia genome encoded the ammonium/nitrite conversion pathway. This links a recovered genome to reactor function without establishing that genome recovery exhaustively identifies every organism contributing to the measured flux.
Participating Taxa: anammox bacterium
Metabolites: ammonium (CHEBI:28938 · MediaIngredientMech · CMMMech), nitrite (CHEBI:16301 · MediaIngredientMech · CMMMech)
Biological Processes:
- nitrogen cycle metabolic process (GO:0071941 · PathwayMech)
HYPOTHESIZED - anammox depends on nitrite, so a guild diverting nitrite could limit its substrate supply; this vulnerability does not by itself establish the cause of the observed crash.
Evidence
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PMID:31980038 - SUPPORT (IN_VITRO)"conversion of ammonium and nitrite to molecular nitrogen "
Core DNRA Nitrite Reduction Capacity
COMPUTATIONAL POTENTIAL - nrfAH annotations identify genomes capable of reducing nitrite to ammonium. DNRA retains fixed nitrogen and could compete with anammox for nitrite; gene capacity does not establish its realized flux or pathway preference.
Participating Taxa: dissimilatory nitrate reducing (DNRA) bacteria
Metabolites: nitrite (CHEBI:16301 · MediaIngredientMech · CMMMech), ammonium (CHEBI:28938 · MediaIngredientMech · CMMMech)
Biological Processes:
- nitrogen cycle metabolic process (GO:0071941 · PathwayMech)
HYPOTHESIZED - if nrfAH-bearing bacteria use the DNRA route, their nitrite consumption could divert substrate from anammox while retaining fixed nitrogen as ammonium. Alternative partial-denitrification routes remain possible.
Evidence
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PMID:31980038 - SUPPORT (COMPUTATIONAL)"DNRA bacteria were considered to be bacteria capable of conversion of nitrite to ammonium using the nrfAH enzymes "
Pre-Crash DNRA Bacterial Replication
PARTIAL - metagenomic coverage-based iRep estimates and compositional log-ratio changes identified DNRA-capable genomes associated with destabilization. Two genomes increased consistently across reference frames and three others only under some comparisons; these estimates are not direct perturbation measurements of competitive growth.
Source Taxon: dissimilatory nitrate reducing (DNRA) bacteria
Target Taxon: anammox bacterium
Biological Processes:
- growth (GO:0040007 · PathwayMech)
PARTIAL - inferred replication and abundance changes preceding collapse support candidate competitors, but do not demonstrate that their growth caused the loss of anammox performance.
Evidence
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PMID:31980038 - PARTIAL (COMPUTATIONAL)"A bacterium was considered to influence the destabilization if it both increased in replication prior to the event and had a positive and significantly high LR "
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PMID:31980038 - PARTIAL (COMPUTATIONAL)"All bacteria that were shown to affect the destabilization event were DNRA bacteria "
Candidate DNRA Competition During Anammox Destabilization
HYPOTHESIZED - the authors infer DNRA competition during destabilization by assuming that organisms encoding alternative routes prefer the higher-energy pathway. Partial denitrification with nitric-oxide leakage is an alternative explanation. The nitrogen-removal crash was measured, but realized pathway dominance and competition were not directly isolated.
Source Taxon: dissimilatory nitrate reducing (DNRA) bacteria
Target Taxon: anammox bacterium
Metabolites: nitrate (CHEBI:17632 · MediaIngredientMech · CMMMech), nitrite (CHEBI:16301 · MediaIngredientMech · CMMMech), ammonium (CHEBI:28938 · MediaIngredientMech · CMMMech)
Biological Processes:
- nitrogen cycle metabolic process (GO:0071941 · PathwayMech)
Evidence
-
PMID:31980038 - PARTIAL (COMPUTATIONAL)"Under this assumption, DNRA was clearly revealed as the dominant process occurring in the bioreactor during the anammox performance destabilization event "
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PMID:31980038 - PARTIAL (COMPUTATIONAL)"Increased replication of bacteria capable of DNRA led to the out-competition of anammox bacteria "
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Did DNRA competition or an alternative nitrite-reduction mechanism cause anammox destabilization?
PMID:31980038 explicitly conditions DNRA dominance on pathway choice and discusses partial denitrification. iRep and compositional changes identify candidates rather than establish causality. Recovery followed increased trace metals, not selective removal of the DNRA guild; direct pathway flux and perturbations remain needed.
Attaches to: ecological_interactions#Nutrient-Acquisition Core Selection, ecological_interactions#Brocadia Ammonium-Nitrite Anammox, ecological_interactions#Core DNRA Nitrite Reduction Capacity, ecological_interactions#Pre-Crash DNRA Bacterial Replication, ecological_interactions#Candidate DNRA Competition During Anammox Destabilization
External Resources
| Name | Repository | Resource ID |
|---|---|---|
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Primary publication for the anammox/DNRA destabilization community
PubMed record for the Keren et al. 2020 Microbiome paper. |
OTHER | PMID:31980038 |
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DOI landing page
DOI link to the Microbiome paper. |
OTHER | doi:10.1186/s40168-020-0786-3 |
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Bioreactor performance state | stable -> destabilized -> recovered | N/A |
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Growth Media
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