M. vaginatus and Massilia sp. METH4 form a resource-trading mutualism under carbon- and nitrogen-limited conditions, with cyanobacterial photosynthate supporting the heterotroph and heterotrophic nitrogen acquisition supporting cyanobacterial growth.
+M. vaginatus PCC 9802 and Massilia sp. METH4 participate in selective carbon-for-nitrogen mutualism: coculture growth under organic-carbon and fixed-nitrogen limitation is consistent with photosynthate supporting the heterotroph and diazotrophic nitrogen acquisition supporting the cyanobacterium. The shared growth phenotype does not by itself identify the transferred organic-carbon compound or quantify partner-specific fluxes.
Source Taxon: Microcoleus vaginatus PCC 9802
@@ -669,7 +669,7 @@In the M. vaginatus PCC 9802-Massilia sp. METH4 coculture, Massilia upregulates urea-biosynthesis functions while M. vaginatus upregulates urea uptake and urea carboxylase/allophanate hydrolase functions, supporting urea as the nitrogen-transfer vehicle.
+PARTIAL - Urea is a strongly supported likely nitrogen-transfer vehicle in the exact PCC 9802/METH4 pair. Coculture increases extracellular urea release; METH4 upregulates urea-cycle genes and PCC 9802 upregulates uptake and urea carboxylase/allophanate hydrolase genes. PCC 9802 can grow on supplied urea down to 5 micromolar, but not 2 micromolar in the tested assay. These convergent results support cross-feeding without directly tracing the origin and assimilation of each urea molecule or proving urea is the exclusive nitrogen carrier. Release rates use total coculture biomass, because a heterotrophic origin of extracellular urea is inferred rather than absolutely resolved.
Source Taxon: Massilia sp. METH4
@@ -714,8 +714,7 @@Massilia urea release supplies the low-concentration nitrogen vehicle that completes the M. vaginatus carbon-for-nitrogen exchange with its heterotrophic partner. -
+PARTIAL - Coculture-associated urea release and cyanobacterial low-concentration urea utilization provide a plausible, experimentally supported route for the nitrogen side of carbon-for-nitrogen trading. Coordinated expression supports Massilia-to-Microcoleus transfer, but exclusive donor attribution and the fraction of growth sustained by this route are not directly resolved.
Nitrogen-starved M. vaginatus and carbon-limited Massilia sp. METH4 produce GABA and glutamate signals that modulate M. vaginatus motility and bundle formation, optimizing close spatial organization for the mutualism.
+GABA and glutamate released by C-limited Massilia sp. METH4 and N-starved M. vaginatus influence cyanobacterial motility and bundling. Addition experiments establish N-dependent chemokinetic and chemophobic responses, not measured Massilia migration; PCC 9802 did not show true chemotaxis to glutamate. Natural-bundle assays additionally measure gliding reversals, a response poorly retained in the long-cultured PCC 9802 strain. Low GABA can stabilize bundles, whereas high GABA can destabilize natural bundles, so increasing signal is not uniformly beneficial. The proposed benefit to carbon-for-nitrogen exchange is spatial retention near heterotrophic partners, not a directly measured flux increase.
Source Taxon: Massilia sp. METH4
@@ -788,12 +787,6 @@Biological Processes:
GABA and glutamate signaling spatially organizes Massilia near nitrogen-starved M. vaginatus, concentrating diazotrophic cyanosphere partners where they can optimize carbon-for-nitrogen exchange. -
+PARTIAL - GABA/glutamate responses keep nitrogen-limited Microcoleus trichomes bundled near cyanosphere partners, providing spatial proximity expected to facilitate nutrient exchange. Signal-addition and cyanosphere-cleansing experiments support bundle organization, but the increase in carbon-for-nitrogen flux or fitness attributable to this organization was not directly quantified. The responding motile organism is Microcoleus, not demonstrated recruitment of motile Massilia.
Retain demonstrated mutualistic growth, urea pool/release changes, supplied-urea growth and signal-induced motility. The wrae246 Results explicitly does not absolutely resolve the urea donor in coculture; total biomass normalizes release. No selective transfer tracing or uc/ah enzyme-affinity characterization establishes an exclusive carrier. The wrad029 experiments distinguish PCC 9802 from natural bundles, chemokinesis/chemophobia from true glutamate chemotaxis, and concentration-dependent stabilization from high-GABA destabilization. Improved nutrient-flux efficiency is the mechanistic interpretation, not an independently quantified endpoint. No new self-loop is inferred from the proposed feedback model.
+ +Attaches to: ecological_interactions#Urea-Mediated Nitrogen Transfer, ecological_interactions#GABA and Glutamate Spatial Signaling
Root-derived bacteria couple nitrification, denitrification, and plant growth promotion to remove ammonia nitrogen.
+The ten-strain root-derived SynCom was selected for nitrification and denitrification capabilities and plant growth promotion in ammonia-nitrogen-polluted REE tailings. The five named participants are the existing grouped taxonomy entries, not five strains or ten fully resolved strain identities. Capability and community-level outcomes do not establish every member contribution or reciprocal microbial fitness benefit.
+Participating Taxa: + + Burkholderia sp., + + Paraburkholderia sp., + + Curtobacterium sp., + + Leifsonia sp., + + Sinomonas sp. + +
+Metabolites: @@ -715,7 +728,7 @@
Nitrifying and denitrifying root-derived strains transform the high ammonia-nitrogen load in REE tailings, reducing pollutant AN in both unplanted and Miscanthus-planted tailing soil.
+PARTIAL - The SynCom nitrogen-cycle capabilities support biological transformation as a contributor to the observed ammonia-nitrogen reduction. The primary abstract attributes removal jointly to microbial transformation and plant-associated uptake; the available evidence does not partition their quantitative contributions or establish every participating strain as necessary.
The live Miscanthus-root SynCom reduced ammonia nitrogen in REE tailing soil, both by itself and more strongly when inoculated with Miscanthus plants.
+The SynCom alone reduced tailing-soil ammonia nitrogen by 24.8%; with Miscanthus the reduction was 32.6%, compared with 25.5% for plants alone. These positive community/plant treatment effects are retained without calling ammonia-nitrogen disappearance a measured complete nitrogen balance, universal strain cooperation or reciprocal fitness gain.
+ + + + +Participating Taxa: + + Burkholderia sp., + + Paraburkholderia sp., + + Curtobacterium sp., + Leifsonia sp., + Sinomonas sp. +
@@ -805,7 +831,7 @@Ammonia-nitrogen transformation by live SynCom cells increases the plant-associated removal effect and accompanies larger Miscanthus shoot and root biomass.
+HYPOTHESIZED - Reduced ammonia-nitrogen stress and altered nitrogen availability could contribute to the shoot/root biomass increase after live SynCom inoculation. The primary abstract reports both outcomes but does not isolate this mediation from other growth-promoting activities or the reverse contribution of larger plants to nitrogen uptake; this arrow is not a selectively demonstrated causal direction.
Live SynCom inoculation significantly increases Miscanthus shoot and root biomass in REE tailings, and plant roots enrich nitrogen-cycle strains that accelerate nitrogen transformation and absorption.
+Live SynCom inoculation increased Miscanthus shoot and root biomass by 39.8% and 49.7%, respectively, relative to dead SynCom inoculation. Seven nitrogen-cycle strains were particularly enriched, consistent with selective root association. These results establish positive inoculation effects and enrichment, not proof that enrichment itself causes biomass gain or a quantitative measurement of plant nitrogen uptake mediated by each strain.
+ + + +Participating Taxa: + Burkholderia sp., + Paraburkholderia sp., + + Curtobacterium sp., + + Leifsonia sp., + + Sinomonas sp. + +
@@ -930,6 +969,25 @@PMID39481489 supports positive AN removal, live-versus-dead biomass gains and enrichment of seven strains. The available primary abstract does not resolve transformation versus uptake contributions or the direction of mediation between AN loss and biomass. Full Methods, supplements and nitrogen-fate controls need inspection; abstract-only access is not evidence those controls were absent. The canonical Sinomonas sp./species-level taxon mismatch is preserved for separate metadata review, and grouped participants do not claim resolved strain-specific activity.
+ +Attaches to: ecological_interactions#Nitrogen Transformation in REE Tailings, ecological_interactions#Live-SynCom Ammonia Nitrogen Removal, ecological_interactions#Miscanthus Biomass Stimulation
Acidithiobacillus thiooxidans oxidizes elemental sulfur and reduced inorganic sulfur compounds to generate sulfuric acid (H₂SO₄), the primary biogenic lixiviant for gallium dissolution from waste LEDs. The sulfur oxidation process (S⁰ + 1.5O₂ + H₂O → H₂SO₄) produces protons that maintain extremely low pH (1.0-1.5) in the bioreactor. This acidic lixiviant is then transferred to the leaching reactor where it attacks gallium nitride (GaN) semiconductor layers in crushed LED waste. The sulfuric acid protonates GaN surfaces and solubilizes gallium according to: GaN + 3H₂SO₄ → Ga³⁺ + NH₄⁺ + 3SO₄²⁻. The non-contact bioleaching design separates microbial acid production from LED leaching, preventing toxic LED components (polymers, epoxies, heavy metals) from inhibiting At. thiooxidans while enabling continuous lixiviant generation. This process achieves remarkable 99.5% gallium recovery in just 3 days at 15 g/L pulp density, far exceeding conventional chemical leaching methods. The biogenic acid also mobilizes copper and nickel from LED interconnects and plating. -
+PARTIAL - The existing 2025 source excerpt attributes sulfuric-acid generation from elemental sulfur to A. thiooxidans in the mixed culture, lowering pH to 1.53. Acid is a reported contributor to gallium leaching, not demonstrated mutualism or a complete member-specific leaching yield. The selected excerpt is retained with provenance limits because the full primary Results was unavailable in this review; unbalanced GaN chemistry and continuous-production claims are not retained.
-Source Taxon: Acidithiobacillus thiooxidans
+Participating Taxa: + Acidithiobacillus thiooxidans +
-Metabolites: - sulfur - (CHEBI:26833), + +
Metabolites: sulfuric acid (CHEBI:26836), - - gallium(3+) - (CHEBI:49631) + class="term-link" target="_blank" rel="noopener noreferrer">CHEBI:26836)
@@ -712,8 +696,8 @@A. thiooxidans-derived sulfuric acid is one of the two biogenic lixiviant components that jointly drive WLED gallium extraction.
+ → Mixed-Consortium Lixiviant Production +PARTIAL - Sulfur oxidation supplies the acid component of the mixed-culture lixiviant. The selected 2025 excerpt supports this production role, not a quantified cooperative effect or independently verified member-removal experiment in the unavailable full Methods.
Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans oxidize ferrous iron (Fe²⁺) to ferric iron (Fe³⁺) in the bioreactor, producing a secondary biogenic oxidant for metal recovery from LED waste. The iron oxidation reaction (2Fe²⁺ + 0.5O₂ + 2H⁺ → 2Fe³⁺ + H₂O) generates Fe³⁺ that enhances dissolution of copper interconnects and nickel plating present in LEDs. Copper dissolution follows: Cu⁰ + 2Fe³⁺ + 4H⁺ → Cu²⁺ + 2Fe²⁺ + 2H₂O, while nickel is solubilized through similar oxidative attack. The Fe³⁺ may also participate in gallium mobilization through redox interactions with GaN semiconductor materials. The mixed consortium design with both At. ferrooxidans and L. ferrooxidans ensures robust iron oxidation across the pH 1.0-1.5 range - At. ferrooxidans provides activity at pH >1.5 while L. ferrooxidans excels at pH <1.5. This complementary pH tolerance maintains continuous Fe³⁺ supply. The non-contact design allows iron oxidizers to function optimally in the bioreactor without exposure to toxic LED materials, while the generated Fe³⁺-rich lixiviant attacks metals in the separate leaching reactor. -
+PARTIAL - Existing 2025 source excerpts identify A. ferrooxidans and L. ferrooxidans as producers of ferric ions from ferrous iron in the mixed community. This supports a joint iron-oxidizing guild contribution, not experimentally resolved pH niche partition, mutual benefit or relative member contributions. The 4-5 g/L stepwise ferric condition in PMID31203122 belongs to a separate adapted A. ferrooxidans system and is not an exact-consortium result.
@@ -782,45 +751,20 @@Biological Processes:
-Ferric ions generated by the two iron oxidizers are the oxidizing lixiviant component paired with biogenic sulfuric acid for gallium extraction.
+ → Mixed-Consortium Lixiviant Production +PARTIAL - Iron oxidation supplies ferric ions as the oxidizing component of the mixed-culture lixiviant. This component relationship is retained from the 2025 excerpts; the separate 2019 single-strain ferric-dosing experiment does not establish its magnitude or guild dependence here.
The 1:1:1 mixed consortium of At. thiooxidans, At. ferrooxidans, and L. ferrooxidans produces synergistic biogenic lixiviants combining sulfuric acid and ferric iron for enhanced gallium and base metal recovery. The three organisms occupy complementary metabolic niches: At. thiooxidans specializes in sulfur oxidation, L. ferrooxidans in iron oxidation at extreme acidity (pH <1.5), and At. ferrooxidans in dual iron/sulfur oxidation at moderate acidity (pH >1.5). This metabolic diversity ensures robust lixiviant production across the full pH 1.0-1.5 operating range. The sulfuric acid from At. thiooxidans maintains low pH essential for Fe³⁺ stability and prevents metal hydroxide precipitation, while simultaneously providing protons for direct GaN dissolution. The Fe³⁺ from At. ferrooxidans and L. ferrooxidans attacks metallic LED components. The consortium achieves 99.5% gallium recovery in 3 days, demonstrating the power of mixed microbial communities for complex metal recovery tasks. Equal ratios (1:1:1) likely optimize the balance between acid generation and oxidant production. -
+PARTIAL - The consortium assembled at an A. thiooxidans:A. ferrooxidans:L. ferrooxidans ratio of 1:1:1 produces a biogenic lixiviant containing sulfuric acid and ferric ions. The source excerpt reports both components contribute to gallium extraction. Joint contribution is not by itself evidence of synergy, optimized inoculum ratio, persistent equal abundance or pH-partitioned coexistence. Selective component and member controls remain to be checked against the complete primary source.
@@ -878,11 +820,7 @@The mixed consortium generates the cell-free sulfuric-acid and ferric-ion lixiviant used for the non-contact WLED leaching stage.
+ → Non-Contact Gallium Recovery +Biogenic lixiviants produced by the mixed culture enable the non-contact gallium leaching endpoint reported for 15 g/L waste LEDs over 3 days. The primary abstract directly supports this functional production-to-recovery connection; it does not quantify separate acid/ferric contributions or demonstrate mutual benefit among the producing organisms.
The non-contact bioleaching process spatially separates microbial lixiviant production from LED waste leaching, enabling optimal performance of both biological and chemical stages. In the bioreactor, the mixed consortium grows on sulfur and iron substrates, generating sulfuric acid and ferric iron without exposure to toxic LED components (polymers, epoxies, brominated flame retardants, heavy metals) that would inhibit bacterial growth and acid production. The acidic, oxidizing lixiviant (pH 1.5 spent lixiviant from bioreactor) is transferred to the leaching reactor where it attacks crushed LED waste at 15 g/L pulp density. After leaching, the pregnant solution containing dissolved gallium, copper, and nickel is separated from solid residues, while depleted lixiviant can be recycled to the bioreactor for regeneration. This two-stage design achieves 99.5% gallium recovery in 3 days, outperforming conventional one-step contact bioleaching or harsh chemical methods. The approach demonstrates how engineered spatial separation can overcome toxicity barriers in microbial metal recovery from complex electronic waste. -
+The mixed-community biogenic lixiviant achieved 99.5% gallium leaching at 15 g/L waste LEDs in 3 days under non-contact conditions, compared with 45.59% during contact bioleaching. This is a positive engineered community output, not a commensal interaction or proof of continuous lixiviant recycling. The primary abstract also reports contact-associated gallium adsorption up to 21.43% and proposes a role for bound extracellular polymers; the component-specific adsorption mechanism and its contribution to the recovery difference remain unresolved.
@@ -977,7 +900,11 @@Preserve the 2025 mixed-community recovery comparison, but keep it separate from the adapted single-strain A. ferrooxidans experiment in PMID31203122 at20 g/L. Selected cached 2025 excerpts retain acid/iron roles with PARTIAL support; content_type:full is not proof that complete Methods were read. Publisher access returned403. The abstract reports Ga adsorption up to21.43% and hypothesizes protein/polysaccharide roles; this does not isolate their contribution to the recovery gap or close a total-Ga balance. Obtain authorized primary Methods and evaluate a distinct adsorption node/edge through the one-record Edison workflow before extending the graph. No paid run or new structure is included here.
+ +Attaches to: ecological_interactions#Biogenic Sulfuric Acid Production for Gallium Leaching, ecological_interactions#Ferric Iron Generation in the Mixed Consortium, ecological_interactions#Mixed-Consortium Lixiviant Production, ecological_interactions#Non-Contact Gallium Recovery