An electroactive microbial community established and maintained for almost four years in microbial electrochemical cells (MXCs) inoculated with a well-studied aquifer near Rifle, CO. Anodes were poised mostly at -0.2 to -0.25 V vs SHE to mimic iron-oxide mineral redox potentials, with acetate as the sole carbon source. Genome-resolved metagenomics of two biofilm and 26 planktonic samples yielded 84 bacterial and 2 archaeal near-complete draft genomes. A novel Geobacter sp. with at least 72 putative multiheme c-type cytochromes dominated the electrode-attached community, while diverse other organisms (Actinobacteria, Ignavibacteria, Chloroflexi, Acidobacteria, Firmicutes, Beta- and Gammaproteobacteria) also encoded multiheme cytochromes, porin-cytochrome complexes, and electrically conductive pili (e-pili), identifying a small subset of Rifle aquifer organisms that may mediate mineral redox transformations.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| novel multiheme-cytochrome Geobacter sp. — ontology label: Geobacter | NCBITaxon:28231 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
SYNTROPHIC_PARTNER
|
DOMINANT |
|
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| EET-capable Rifle aquifer Actinobacteria — ontology label: Actinomycetota | NCBITaxon:201174 · TaxonMech · TraitMech |
SYNTROPHIC_PARTNER
|
N/A |
|
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| EET-capable Rifle aquifer Ignavibacteria — ontology label: Ignavibacteriota | NCBITaxon:1134404 · TaxonMech · TraitMech |
SYNTROPHIC_PARTNER
|
N/A |
|
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| EET-capable Rifle aquifer Chloroflexi — ontology label: Chloroflexota | NCBITaxon:200795 · TaxonMech · TraitMech |
SYNTROPHIC_PARTNER
|
N/A |
|
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| EET-capable Rifle aquifer Acidobacteria — ontology label: Acidobacteriota | NCBITaxon:57723 · TaxonMech · TraitMech |
SYNTROPHIC_PARTNER
|
N/A |
|
|||
| EET-capable Rifle aquifer Firmicutes — ontology label: Bacillota | NCBITaxon:1239 · TaxonMech · TraitMech |
SYNTROPHIC_PARTNER
|
N/A |
|
|||
| EET-capable Rifle aquifer Beta- and Gammaproteobacteria — ontology label: Pseudomonadota | NCBITaxon:1224 · TaxonMech · TraitMech |
SYNTROPHIC_PARTNER
|
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.
Acetate-Fed Iron-Oxide-Like Bioanode Selection
Acetate-fed microbial electrochemical cells enriched electroactive consortia from Rifle aquifer material. Electrode-attached biofilm and planktonic communities differed, and the systems produced current. This is an observed community response to the enrichment environment, not proof that every member directly respires the anode or occupies a demonstrated partitioned niche.
Metabolites: acetate (CHEBI:30089 · MediaIngredientMech · CMMMech)
Biological Processes:
- anaerobic respiration (GO:0009061 · PathwayMech)
- electron transport chain (GO:0022900 · PathwayMech)
PARTIAL: the acetate-fed electrode environment enriched a biofilm dominated by the novel Geobacter population. The observed enrichment supports selection in this system, but does not establish competitive exclusion, a single causal contribution of its MHC inventory or dominance throughout the natural aquifer.
Evidence
-
PMID:32849356 - SUPPORT (IN_VITRO)"Electroactive biofilms were established and maintained for almost 4 years"
Multiheme Geobacter Electrode Dominance
A novel Geobacter population dominated the sampled electrode-attached community, and its recovered genome encoded at least 72 putative multiheme c-type cytochromes. This combines observed biofilm composition with predicted genomic capacity; it does not establish competition, conductivity of each candidate protein or the organism's natural aquifer niche.
Participating Taxa: novel multiheme-cytochrome Geobacter sp.
Evidence
-
PMID:32849356 - SUPPORT (IN_VITRO)"A novel Geobacter sp. with at least 72 putative multiheme c-type cytochromes (MHCs) was the dominant electrode-attached organism "
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which genomic candidates actually mediate environmental EET or interspecies feedback?
The complete primary main text supports community current, enrichment and biofilm dominance. Non-Geobacter MHCs, candidate PCCs, e-pili and OmcS homologs are valuable genomic predictions, not demonstrated niche partitioning, conductivity, mineral flux or syntrophic partnerships. The candidate-set conclusion does not exclude EET potential in all other aquifer organisms. Remove four inventory/conclusion nodes and three analysis-order arrows while preserving the environmental-selection observation and one PARTIAL dominance direction. The source leaves the dominant organism's environmental niche unresolved and gives inconsistent near-complete-genome denominators in the PCC caption versus main text; no denominator is silently adjudicated. Non-graph functional-role labels and canonical taxonomy remain issue1764; cultivation setup is unchanged.
Attaches to: ecological_interactions#Acetate-Fed Iron-Oxide-Like Bioanode Selection, ecological_interactions#Multiheme Geobacter Electrode Dominance
1 evidence item(s)
may have the potential to mediate mineral redox transformations
The primary abstract explicitly describes potential, not experimentally measured natural-community flux.
External Resources
| Name | Repository | Resource ID |
|---|---|---|
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Primary publication for the Rifle bioanode community
PubMed record for the Arbour et al. 2020 Frontiers in Microbiology paper. |
OTHER | PMID:32849356 |
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DOI landing page
DOI link to the Frontiers in Microbiology paper. |
OTHER | doi:10.3389/fmicb.2020.01694 |
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Anode redox potential | -0.2 to -0.25 V vs SHE | N/A |
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| Operating duration | nearly 4 years of continuous operation | N/A |
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