A specialized mixotrophic microbial consortium enriched in a continuous electrostimulated bioreactor operated at a constant potential of 300 mV for CO2 conversion into volatile fatty acids. Decreasing hydraulic retention time (HRT) selected for a spatially organized community in which Enterococcus and Clostridium dominated the planktonic phase while Desulfovibrio and Enterococcus were enriched in the electrode biofilm. This syntrophic organization enhanced biomass-specific inorganic carbon removal and redirected carbon flux toward acetate, a key product of acetogenic pathways, with electrode-associated taxa contributing reducing equivalents that supported autotrophic CO2/HCO3- fixation.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Enterococcus | NCBITaxon:1350 · TaxonMech · TraitMech |
SECONDARY_FERMENTER
SYNTROPHIC_PARTNER
|
N/A |
|
|||
| Clostridium | NCBITaxon:1485 · TaxonMech · TraitMech |
PRIMARY_PRODUCER
SYNTROPHIC_PARTNER
|
N/A |
|
|||
| Desulfovibrio | NCBITaxon:872 · TaxonMech · TraitMech |
ELECTROTROPH
SYNTROPHIC_PARTNER
|
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.
HRT-Driven Mixotrophic Consortium Enrichment
A single electrostimulated reactor underwent sequential HRT phases and intervening batch assays. Its changing composition and outputs support an operational association, not an independently replicated HRT-only effect. Participants are representative genera, not the complete enrichment roster.
Participating Taxa: Enterococcus, Clostridium, Desulfovibrio
Metabolites: carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech), acetate (CHEBI:30089 · MediaIngredientMech · CMMMech)
PARTIAL - altered residence time may select community composition, but sequential operation and batch interruptions do not isolate its contribution to the endpoint compartment difference.
Evidence
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doi:10.21203/rs.3.rs-9518331/v1 - SUPPORT (IN_VITRO)"A continuous electrostimulated bioreactor was operated at a constant potential of 300 mV for approximately 1200 h under three HRTs"
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doi:10.21203/rs.3.rs-9518331/v1 - SUPPORT (IN_VITRO)"Decreasing HRT promoted the enrichment of a specialized mixotrophic consortium"
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doi:10.21203/rs.3.rs-9518331/v1 - SUPPORT (IN_VITRO)"Reducing HRT enhanced inorganic carbon utilization and selectively increased acetate production"
Planktonic and Electrode-Biofilm Spatial Partitioning
Endpoint planktonic and electrode-biofilm profiles differed. Relative abundance does not demonstrate taxon-specific flux, physiological niche exclusion or required partner exchange.
Participating Taxa: Enterococcus, Clostridium, Desulfovibrio
HYPOTHESIZED - compartment-associated exchange of reducing equivalents could support carbon uptake. Composition and bulk chemistry do not selectively establish that architecture as the cause of IC removal.
Evidence
-
doi:10.21203/rs.3.rs-9518331/v1 - SUPPORT (IN_VITRO)"Enterococcus and Clostridium dominating the planktonic phase and Desulfovibrio and Enterococcus enriched in the electrode biofilm"
Electrode-Biofilm Carbon-Fixation Pathway Enrichment
PICRUSt2 inferred carbon-fixation potential from amplicon composition. This is not measured gene expression, electron transfer, hydrogen production or pathway flux; the prediction is not itself a causal actor.
Participating Taxa: Enterococcus, Clostridium, Desulfovibrio
Metabolites: carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech), bicarbonate (CHEBI:17544 · MediaIngredientMech · CMMMech)
Evidence
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doi:10.21203/rs.3.rs-9518331/v1 - SUPPORT (COMPUTATIONAL)"Functional predictions further revealed the enrichment of carbon fixation pathways, particularly in the electrode-associated biofilm"
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doi:10.21203/rs.3.rs-9518331/v1 - PARTIAL (COMPUTATIONAL)"electrode-associated taxa contributed to the generation of reducing equivalents and supported autotrophic metabolism"
Biomass-Specific Inorganic Carbon Removal Increase
Biomass-specific inlet/outlet inorganic-carbon removal increased 2.6-fold. This bulk endpoint does not identify assimilation, product fate or a responsible taxon, and is not an independently established cause of acetate output.
Participating Taxa: Enterococcus, Clostridium, Desulfovibrio
Metabolites: carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech), bicarbonate (CHEBI:17544 · MediaIngredientMech · CMMMech), acetate (CHEBI:30089 · MediaIngredientMech · CMMMech)
Evidence
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doi:10.21203/rs.3.rs-9518331/v1 - PARTIAL (IN_VITRO)"This syntrophic organization enhanced biomass-specific IC removal by 2.6-fold"
Acetate-Directed Carbon Flux
Acetate accumulated during reactor operation. Excess over the chosen heterotrophic stoichiometric model is consistent with additional routes, not a measured autotrophic fraction or demonstrated donor-to-recipient cross-feeding.
Participating Taxa: Enterococcus, Clostridium, Desulfovibrio
Metabolites: carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech), bicarbonate (CHEBI:17544 · MediaIngredientMech · CMMMech), acetate (CHEBI:30089 · MediaIngredientMech · CMMMech)
Evidence
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doi:10.21203/rs.3.rs-9518331/v1 - SUPPORT (IN_VITRO)"redirected carbon flux toward acetate, a key product of acetogenic pathways"
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doi:10.21203/rs.3.rs-9518331/v1 - SUPPORT (IN_VITRO)"Acetate reached 1470 mg L"
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doi:10.21203/rs.3.rs-9518331/v1 - PARTIAL (IN_VITRO)"the acetate exceeded heterotrophic stoichiometry, indicating additional CO"
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which exchanges and carbon sources causally account for the reactor endpoints?
Retain two qualified links; remove composition-to-prediction, prediction-to-acetate and IC-removal-to-acetate arrows. Derived annotations and correlated endpoints do not establish mediation. Resolve carbon accounting and selective perturbations before assigning member fluxes. The primary preprint body was read from a public mirror, not separate supplements or visual figures. Non-graph protocol and role claims remain #1434; the recurrent Enterococcus_B grounding is tracked by reopened #373. Canonical NCBI participants are preserved without endorsing GTDB metadata.
Attaches to: ecological_interactions#HRT-Driven Mixotrophic Consortium Enrichment, ecological_interactions#Planktonic and Electrode-Biofilm Spatial Partitioning, ecological_interactions#Electrode-Biofilm Carbon-Fixation Pathway Enrichment, ecological_interactions#Biomass-Specific Inorganic Carbon Removal Increase, ecological_interactions#Acetate-Directed Carbon Flux
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