Engineered anaerobic batch-culture consortium pairing activated anammox sludge from a full-scale municipal wastewater process with an nrfA-deficient Shewanella oneidensis MR-1 mutant. The Delta nrfA strain was inoculated into nitrate- and ammonium-containing mixed medium with sludge from an up-flow anaerobic sludge blanket reactor; blocking the terminal nitrite-to-ammonium DNRA step favored nitrite accumulation, enriched Candidatus Brocadia anammox bacteria, and made the 5:1 anammox-sludge-to-mutant culture the fastest and highest total-nitrogen removal treatment at 97%.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Delta nrfA Shewanella oneidensis MR-1 — ontology label: Shewanella oneidensis MR-1 | NCBITaxon:211586 · TaxonMech · TraitMech | N/A | |
|
|||
| Candidatus Brocadia anammox bacteria — ontology label: Planctomycetota | NCBITaxon:203682 · TaxonMech · TraitMech | N/A | |
|
|||
| endogenous activated-sludge heterotrophic bacteria — ontology label: Bacteria | NCBITaxon:2 · TaxonMech · TraitMech | N/A | |
|
|||
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.
Delta nrfA nitrate-to-nitrite supply for anammox
CROSS_FEEDINGPARTIAL: the nrfA-deficient Shewanella treatment enhanced nitrate-to-nitrite conversion in the sludge consortium, consistent with supplying anammox substrates. Brocadia and anammox-gene enrichment support this interpretation, but final-time metagenomic abundance is not expression or a taxon-resolved flux measurement. Liquid nitrogen profiles do not separately quantify anammox, denitrification and DNRA contributions or establish that all removed nitrogen followed the proposed pairwise route.
Source Taxon: Delta nrfA Shewanella oneidensis MR-1
Target Taxon: Candidatus Brocadia anammox bacteria
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:42655905 - SUPPORT (IN_VITRO)"all experimental groups achieved 100% NO 3 − ‐N removal efficiency"
-
PMID:42655905 - SUPPORT (IN_VITRO)"the addition of ΔnrfA S. oneidensis MR‐1 enhanced the reduction of NO 3 − ‐N to NO 2 − ‐N"
-
PMID:42655905 - SUPPORT (COMPUTATIONAL)"Crucially, the ΔnrfA mutant may effectively block the terminal reduction of nitrite to ammonium via the Nap/Nrf pathway."
-
PMID:42655905 - SUPPORT (COMPUTATIONAL)"Metagenomic analysis revealed that this configuration enriched anammox bacteria (Candidatus Brocadia ) and enhanced the abundance of key anammox genes ( hzs and hdh )"
Mutant dosage window for anammox performance
The tested mutant-addition series showed context-dependent nitrogen-removal performance, with the reported 5:1 sludge-to-mutant culture-volume treatment reaching 97% total-nitrogen removal. Higher mutant culture fractions had less favorable ammonium/nitrite profiles. HYPOTHESIZED: the authors attribute this pattern partly to ecological competition, but the comparisons do not isolate competition from other community and substrate effects. The ratio is a culture-volume ratio, not a cell-number ratio or universal optimum.
Participating Taxa: Delta nrfA Shewanella oneidensis MR-1, Candidatus Brocadia anammox bacteria, endogenous activated-sludge heterotrophic bacteria
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:42655905 - SUPPORT (IN_VITRO)"Final NH 4 + ‐N levels in ΔB4 and ΔB5 were higher than in ΔCK1"
-
PMID:42655905 - SUPPORT (IN_VITRO)"an excessive proportion of ΔnrfA S. oneidensis MR‐1 could compete with anammox bacteria for ecological niches"
-
PMID:42655905 - SUPPORT (IN_VITRO)"ΔB1 achieved the highest TN removal efficiency (97%) and reached above 90% removal faster"
-
PMID:42655905 - SUPPORT (IN_VITRO)"ΔB1 exhibited the optimal N removal performance, which corresponded to a volumetric ratio of anammox sludge to ΔnrfA S. oneidensis MR‐1 of 5:1"
Knowledge gaps & discussions (2)
KNOWLEDGE_GAP OPEN Which endogenous sludge populations directly exchanged nitrite or electrons with the Delta nrfA S. oneidensis mutant, and does the optimized 5:1 phenotype remain stable in a continuous reactor?
The source profiled the final time point by metagenomics and reported the dominant anammox genus, but it did not isotope-trace nitrate, nitrite, or ammonium flux through the mutant, Brocadia, and endogenous denitrifiers. Its Perspective explicitly calls for long-term continuous trials, gaseous-nitrogen measurements, time-series metagenomics, and isotope labeling to resolve those mechanisms.
Attaches to: taxonomy#endogenous activated-sludge heterotrophic bacteria, ecological_interactions#Delta nrfA nitrate-to-nitrite supply for anammox
3 evidence item(s)
Future long‐term continuous reactor trials are required to evaluate the stable performance of the coupled system under practical running conditions
Names the unresolved need for continuous-reactor validation.
Subsequent tests should quantify gaseous nitrogen metabolites alongside liquid nitrogen pollutants
Names the unresolved nitrogen-product partitioning gap.
future research could carry out isotope labeling tests to quantitatively differentiate the contribution of anammox, denitrification, and DNRA
Names the unresolved isotope-flux attribution gap.
KNOWLEDGE_GAP OPEN Which mechanisms account for the mutant-addition performance gradient?
The dose-response outcome is measured, while competition for ecological niches is an interpretation of mixed-sludge chemistry and community profiles. The existing discussion already records unresolved pathway flux and continuous-reactor stability. Neither bulk removal nor gene abundance identifies a unique inhibitory mechanism at higher mutant fractions.
Attaches to: ecological_interactions#Delta nrfA nitrate-to-nitrite supply for anammox, ecological_interactions#Mutant dosage window for anammox performance
1 evidence item(s)
an excessive proportion of ΔnrfA S. oneidensis MR‐1 could compete with anammox bacteria for ecological niches
Supports an explicitly proposed competition interpretation, not an isolated competitive mechanism.
External Resources
| Name | Repository | Resource ID |
|---|---|---|
|
Primary publication for the Delta nrfA Shewanella-anammox consortium
PubMed record for Yi et al. 2026 Water Environment Research article on nrfA-deficient S. oneidensis MR-1 coupled with anammox sludge. |
OTHER | PMID:42655905 |
|
||
|
DOI landing page
DOI link to the Water Environment Research article. |
OTHER | doi:10.1002/wer.70526 |
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Anammox sludge to Delta nrfA Shewanella inoculation ratio | 5:1 | mL:mL culture volume in optimized Delta B1 |
|
||
Growth Media
Cross-Mech Suite Links
Explore related entities across the CultureBotAI X-Mech knowledge bases: