C. autoethanogenum converts CO or syngas into acetate and ethanol, producing the substrates that support chain elongation by C. kluyveri.
+C. autoethanogenum converts CO or syngas to acetate and ethanol that support C. kluyveri chain elongation. Product profiles and pure-culture comparisons support this cross-feeding model. In the 2019 chemostat study, partner ethanol production and electron allocation in coculture were reverse-calculated from measured chain-elongated products and assumed stoichiometry, not directly measured partner-specific fluxes.
Source Taxon: Clostridium autoethanogenum
@@ -698,13 +703,15 @@C. kluyveri consumes ethanol and acetate produced by C. autoethanogenum, enabling formation of butyrate, caproate, butanol, and hexanol from CO or syngas.
+C. kluyveri uses ethanol and acetate for chain elongation to butyrate and caproate, which can supply C. autoethanogenum for reduction to butanol and hexanol. The 2016 study demonstrated acid formation by C. kluyveri and higher-alcohol formation by acid-supplemented C. autoethanogenum pure cultures. Higher alcohols are therefore coculture products, not products assigned to C. kluyveri alone; this attribution is bounded to the tested conditions.
Source Taxon: Clostridium kluyveri
+Target Taxon: Clostridium autoethanogenum
+Metabolites: @@ -788,10 +795,9 @@
C. kluyveri removal of ethanol during co-cultivation shifts C. autoethanogenum metabolism toward solventogenesis, improving the electron flow into chain-elongated products.
+HYPOTHESIZED - ethanol consumption by C. kluyveri lowers its extracellular concentration and thermodynamically favors further ethanol formation by C. autoethanogenum. Chemostat products, reverse-calculated ethanol flux, hydrogen and acetate additions, and the absence of a major uniform central-metabolism transcript response support this interpretation. They do not exclude protein abundance or post-translational regulation. This node represents a proposed feedback effect of product removal, not ethanol donation from C. kluyveri to the acetogen.
Source Taxon: Clostridium kluyveri
@@ -830,8 +836,7 @@Continuous ethanol removal by C. kluyveri pulls C. autoethanogenum metabolism toward solventogenesis and improves electron flow from CO or syngas into chain-elongated products. -
+HYPOTHESIZED - C. kluyveri consumption keeps ethanol low and could favor C. autoethanogenum solventogenesis, supplying further ethanol for chain elongation. Stoichiometric flux estimates and perturbations support this feedback model, but do not uniquely establish thermodynamics as its mediator.
PMID:31792266 combines measured product pools, stoichiometric reverse-calculation, transcriptomics and hydrogen/acetate perturbations. The thermodynamic explanation is supported but not exclusive. Selective ethanol-removal perturbations with partner-resolved flux and protein-level measurements would distinguish it from alternative regulation. PMID:33240469 remains computational support, not a new experimentally demonstrated interaction.
+ +Attaches to: ecological_interactions#Acetogenic CO and Syngas Fermentation, ecological_interactions#Ethanol-Driven Chain Elongation, ecological_interactions#Proposed thermodynamic ethanol pull by C. kluyveri
Nitrogen, sulfur, phosphate, and vitamin loads were reduced into a low-ionic-strength defined minimal medium that supported cellobiose, cellulose, acid-pretreated Populus, and the cellulose/xylan coculture condition used to maintain both thermophilic cellulolytic bacteria. -
+A low-ionic-strength defined medium with reduced nitrogen, sulfur, phosphate and vitamin supplements was developed after nutrient-response experiments. The primary abstract reports cellobiose, cellulose and acid-pretreated Populus fermentation and separately reports coculture maintenance on cellulose/xylan substrates. These statements do not establish that every substrate or nutrient-response experiment used the coculture. Medium development is cultivation context, not demonstrated partner-to-partner colonization facilitation.
@@ -644,29 +637,7 @@Biological Processes:
-The reduced defined medium was the chemical setting in which the C. thermocellum and C. bescii populations were maintained together. -
-The two bacterial populations were maintained together in the defined medium when the coculture was supplied with cellulose and xylan, showing compatible coexistence under mixed-polysaccharide conditions.
+Both populations were reported to be maintained in cocultures on substrates containing cellulose and xylan in defined medium with sulfate and basal vitamins. This is an observed co-maintenance endpoint. The accessible exact-system abstract does not resolve the duration, population trajectories or perturbations needed to establish long-term stability, reciprocal benefit, colonization facilitation or a unique maintenance mechanism.
@@ -738,23 +708,6 @@Biological Processes:
-C. thermocellum provides cellulolytic growth on crystalline cellulose, while C. bescii DSM 6725 has genome-supported capacity to use multiple plant polysaccharides, including cellulose- and xylan-associated responses that make it relevant to mixed lignocellulose substrates.
+Separate member-level evidence supports plant-polysaccharide conversion: C. thermocellum was grown on crystalline cellulose in the nutrient study, and C. bescii DSM 6725 was studied by genome analysis plus experimental transcriptomics and proteomics on polysaccharide substrates. Cellulose-responsive expression and cellulose/xylan-associated proteins are measured results, while functions of some hypothetical proteins remain inferred. These member assays do not demonstrate niche partitioning, interspecies substrate transfer or mediation of coculture maintenance.
@@ -869,7 +821,7 @@PMID:23306120 is abstract-bounded in this review; its full body was not obtained through the attempted public routes. The abstract reports maintenance, not its duration or an isolated ecological mechanism. PMID:21227922 contains empirical C. bescii molecular responses as well as genomic inference, but does not test this coculture. Full-method access and partner-resolved time courses are needed before claiming nutrient-reduction causality, stability or niche partitioning. The earlier removed capacity-to-maintenance arrow remains absent.
+ +Attaches to: ecological_interactions#Reduced-Nutrient Defined Cellulose-Xylan Medium, ecological_interactions#Observed Co-Maintenance On Cellulose And Xylan, ecological_interactions#Thermophilic Plant-Polysaccharide Conversion Capacity
C. carboxidivorans provides acetate and ethanol from CO/CO2 gas fermentation, while C. kluyveri uses these C2 products for chain elongation to organic acids. -
+C. carboxidivorans produces acetate and ethanol from CO/CO2 gas fermentation, supplying C. kluyveri chain elongation to butyrate and hexanoate. Exact-pair batch product profiles and the continuous cascade support this cross-feeding model. Restricted C. kluyveri growth at high CO does not mean absence of chain-elongation activity, and C. carboxidivorans can also form C4/C6 products under appropriate conditions.
Source Taxon: Clostridium carboxidivorans
@@ -706,8 +705,7 @@Organic acids formed by C. kluyveri are reduced by C. carboxidivorans to alcohols, increasing butanol and enabling hexanol production relative to C. carboxidivorans monoculture. -
+C. kluyveri-derived organic acids supply C. carboxidivorans for reduction to butanol and hexanol. At pH 6.0 and 800 mbar inlet CO, the 144-hour batch coculture had about three times the final butanol and detectable hexanol relative to its matched acetogen-only control. This is a condition-specific comparison, not universal monoculture incapacity: the cascade study also measured alcohol production with C. carboxidivorans alone. Acid reduction contributes to output alongside de novo alcohol synthesis by the acetogen.
Source Taxon: Clostridium kluyveri
@@ -725,8 +723,8 @@In the continuous reactor cascade, lower CO and sulfide supply supported growth and chain elongation in the first reactor, while higher CO in the second reactor supported organic-acid reduction and de novo C2-C6 alcohol synthesis. -
+The engineered continuous cascade used a first reactor at pH 6.0, 100 mbar inlet CO and added sulfide, followed by a second reactor at pH 5.0 and 800 mbar inlet CO. Gas flow and dilution rate also differed. The first stage supported growth and chain elongation; the second supported organic-acid reduction and de novo alcohol synthesis, while C. kluyveri growth was negligible. This is a measured process configuration, not evidence of ecological niche partitioning or an isolated CO-only effect.
@@ -830,8 +826,7 @@Partitioning the cascade into lower-CO chain elongation and higher-CO acid-reduction stages favors the C. carboxidivorans reduction of chain-elongated acids into C2-C6 alcohols. -
+The first stage supplies chain-elongated organic acids to the second, whose combined pH-5.0/high-CO conditions support C. carboxidivorans reduction to alcohols. Product balances also indicate de novo alcohol synthesis, so downstream alcohol output is not all explained by reduction of incoming acids; the design does not isolate the contribution of CO from the other changed operating conditions.
PMID:37110426 changes several operating conditions between cascade stages. Matched monoculture and coculture products support the process outcomes, but do not isolate each control variable or trace every carbon flux. Its abstract states complete C. kluyveri growth inhibition at 100 mbar CO; Results instead report an 86% maximum-biomass reduction there and complete inhibition at 800 mbar, while chain elongation continues. Keep this source discrepancy and growth/activity distinction explicit. Partner-resolved flux and factorial controls would separate these contributions.
+ +Attaches to: ecological_interactions#Acetogen-Chain Elongator Product Coupling, ecological_interactions#Organic Acid Reduction to Longer-Chain Alcohols, ecological_interactions#Engineered CO and pH staging of chain elongation and alcohol formation