A defined two-member cellulose-to-biohydrogen coculture combining the cellulolytic dark-fermentative bacterium Clostridium cellulovorans 743B with the purple nonsulfur photosynthetic bacterium Rhodopseudomonas palustris CGA009. The coculture links cellulose degradation, volatile-fatty-acid exchange, pH stabilization, and photofermentative hydrogen production. It is DOE-relevant as a genetically tractable model for lignocellulosic bioenergy, integrated dark/photo fermentation, and mechanistic design of biohydrogen consortia.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Clostridium cellulovorans 743B | NCBITaxon:573061 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
CROSS_FEEDER
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ABUNDANT |
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| Rhodopseudomonas palustris CGA009 | NCBITaxon:258594 · TaxonMech · TraitMech |
CROSS_FEEDER
PRIMARY_PRODUCER
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ABUNDANT |
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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.
VFA Cross-Feeding and pH Stabilization
CROSS_FEEDINGC. cellulovorans supplies VFAs to R. palustris in illuminated cellulose-fed coculture. PARTIAL - the measured pH and substrate profiles support product-removal feedback, but do not isolate pH as its only mediator. Cellulose is the upstream substrate, not a compound directly donated to R. palustris.
Source Taxon: Clostridium cellulovorans 743B
Target Taxon: Rhodopseudomonas palustris CGA009
Metabolites: cellulose (CHEBI:18246 · MediaIngredientMech · CMMMech), acetate (CHEBI:30089 · MediaIngredientMech · CMMMech)
Biological Processes:
- cellulose catabolic process (GO:0030245 · PathwayMech)
- fermentation (GO:0006113 · PathwayMech)
VFA supply supports R. palustris photofermentation. PARTIAL - acid consumption can also sustain fermenter activity through a smaller pH decline; partner fluxes and the separate contributions of these routes are not directly resolved.
Evidence
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doi:10.1128/AEM.00789-16 - PARTIAL (IN_VITRO)"genes related to biosynthesis of volatile fatty acids (VFAs) in C. cellulovorans were upregulated"
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doi:10.1128/AEM.00789-16 - PARTIAL (IN_VITRO)"a gene that mediates organic compound catabolism in R. palustris was also upregulated"
Integrated Dark and Photo Fermentation for Hydrogen
Coculture hydrogen output exceeded C. cellulovorans monoculture output. PARTIAL - ammonium suppression supports R. palustris nitrogenase involvement in the enhancement, not a directly measured partition of all hydrogen between partners. Nitrogenase-associated proton reduction is not itself evidence of N2 fixation under the argon headspace.
Metabolites: dihydrogen (CHEBI:18276 · MediaIngredientMech · CMMMech), cellulose (CHEBI:18246 · MediaIngredientMech · CMMMech)
Biological Processes:
- photosynthesis (GO:0015979 · PathwayMech)
Evidence
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doi:10.1128/AEM.00789-16 - SUPPORT (IN_VITRO)"consistent with the physiological observations of enhanced H 2 production and cellulose degradation"
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doi:10.1128/AEM.00789-16 - PARTIAL (IN_VITRO)"the enhanced H 2 yield was contributed mainly by R. palustris"
Transcriptomic Responses Associated with Cocultivation
Cellulosomal and nitrogenase-related transcription changes accompany cocultivation. They are measured responses, not demonstrated metabolite exchange or a selectively established cause of the hydrogen phenotype.
Biological Processes:
- cellulose catabolic process (GO:0030245 · PathwayMech)
Evidence
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doi:10.1128/AEM.00789-16 - SUPPORT (IN_VITRO)"nitrogen fixation genes in R. palustris and the cellulosomal genes in C. cellulovorans were upregulated"
Associated Datasets
| Dataset | Type | Repository | Accession |
|---|---|---|---|
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Cellulose-concentration physiology publication for C. cellulovorans-R. palustris coculture
Primary physiology paper establishing the exact C. cellulovorans 743B and R. palustris CGA009 cellulose-fed biohydrogen coculture. |
PHENOTYPE | OTHER | doi:10.1016/j.ijhydene.2015.05.135 |
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Transcriptomic publication for the same C. cellulovorans-R. palustris coculture
Follow-up transcriptomics paper using the same exact C. cellulovorans 743B and R. palustris CGA009 cellulose-grown coculture. |
METATRANSCRIPTOMICS | OTHER | doi:10.1128/AEM.00789-16 |
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN How much of the hydrogen enhancement is mediated by nitrogenase activity and pH-dependent product-removal feedback?
The ammonium intervention supports nitrogenase involvement. Partner-resolved flux and matched-pH or selective pathway interventions would distinguish the remaining mechanisms. Monoculture carbon substrates differ; the transcriptomic model is inferential.
Attaches to: ecological_interactions#VFA Cross-Feeding and pH Stabilization, ecological_interactions#Integrated Dark and Photo Fermentation for Hydrogen, ecological_interactions#Transcriptomic Responses Associated with Cocultivation
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Renewable cellulose substrate | cellulose-grown coculture | N/A |
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| Coculture VFA gradient | VFA concentration gradient | N/A |
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Growth Media
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