A natural cyanobacterial-heterotrophic consortium dominated by Candidatus Phormidium alkaliphilum, isolated from soda lakes. This consortium represents a robust, stable community optimized for carbon sequestration in high-pH environments (pH >11). The community includes 8-12 core members with 29 identified heterotrophic metagenome-assembled genomes spanning Bacteroidota, Alphaproteobacteria, Gammaproteobacteria, Verrucomicrobiota, Patescibacteria, and Planctomycetota. The consortium demonstrated exceptional stability with 4 years of crash-free growth in laboratory culture, maintaining biomass productivity of 15.2 g/m²/day. Ecological interactions include carbon transfer from cyanobacteria to heterotrophs, nutrient remineralization, vitamin provision (B12, B1, B7), and functional niche partitioning that enhances community robustness. The consortium enables direct CO2 capture from air at alkaline pH, making it highly relevant for biotechnological carbon sequestration applications. Stable isotope probing with ¹³C-bicarbonate revealed tight coupling of carbon flux from primary production to heterotrophic populations, particularly Wenzhouxiangella species.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Candidatus Phormidium alkaliphilum — ontology label: Candidatus Sodalinema alkaliphilum | NCBITaxon:3723519 · TaxonMech · TraitMech |
PRIMARY_PRODUCER
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DOMINANT |
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| Wenzhouxiangella sp. | NCBITaxon:1979961 · TaxonMech · TraitMech |
CROSS_FEEDER
SECONDARY_FERMENTER
|
ABUNDANT |
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| Bacteroidota members — ontology label: Bacteroidota | NCBITaxon:976 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
SECONDARY_FERMENTER
|
COMMON |
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| Alphaproteobacteria members — ontology label: Alphaproteobacteria | NCBITaxon:28211 · TaxonMech · TraitMech |
CROSS_FEEDER
SYNTROPHIC_PARTNER
|
COMMON |
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| Verrucomicrobiota members — ontology label: Verrucomicrobiota | NCBITaxon:74201 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
|
COMMON |
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| Planctomycetota members — ontology label: Planctomycetota | NCBITaxon:203682 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
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COMMON |
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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.
Photosynthetic CO2 Fixation
Ca. P. alkaliphilum is the primary producer in this alkaline consortium. Label from supplied 13C-bicarbonate entered cyanobacterial proteins and subsequently heterotrophic proteins. Preserve photosynthetic carbon input without assigning every proposed release route (excretion, vesicles, lysis or osmotic shock) as measured in this community, or treating all cultures as uniformly above pH 11.
Source Taxon: Candidatus Phormidium alkaliphilum
Metabolites: carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech), dissolved organic matter (CHEBI:50860 · MediaIngredientMech · CMMMech)
Biological Processes:
- photosynthesis (GO:0015979 · PathwayMech)
- carbon fixation (GO:0015977 · PathwayMech)
Cyanobacterial fixation supplies carbon subsequently incorporated into heterotrophic proteins, as supported by 13C-bicarbonate protein/SIP. Preserve this experimental donor-to-heterotroph direction without claiming that labeling identifies the exact exchanged compounds or a trophic cascade.
Evidence
-
doi:10.3389/fmicb.2022.780346 - SUPPORT (IN_VITRO)"tight coupling of carbon transfer from cyanobacteria to the heterotrophic populations"
Carbon Transfer to Heterotrophs
CROSS_FEEDINGProtein/SIP supports cyanobacterial carbon transfer to heterotrophs, with strong peptide coverage for Wenzhouxiangella MAG57 and Phycisphaerales MAG34. These populations lagged cyanobacterial labeling, consistent with use of macromolecular carbon; specific protein/glycogen transfer remains an interpretation. Planctomycetota is the existing broad canonical grounding for MAG34, not evidence that every member of that phylum participates. Do not assign all proposed fermentation products to Wenzhouxiangella or infer nutrient return and reciprocal fitness from carbon uptake.
Participating Taxa: Candidatus Phormidium alkaliphilum, Wenzhouxiangella sp., Planctomycetota members
Evidence
-
doi:10.3389/fmicb.2022.780346 - SUPPORT (IN_VITRO)"tight coupling of carbon transfer from cyanobacteria to the heterotrophic populations"
Proposed Cyanobacterial Polymer Use by Verrucomicrobiota
CROSS_FEEDINGPARTIAL - The four Verrucomicrobiota MAGs encode multiple glycoside hydrolases and sulfatases, supporting a proposed niche consuming cyanobacterial sulfated glycopolymers. Gene content is not a direct substrate-use or transfer assay. Low-peptide isotope signals are compatible with heterotrophic carbon assimilation but do not identify polymers as the substrate. No Planctomycetota-to-Verrucomicrobiota transfer or benefit from removal of inhibitory polymers was established.
Source Taxon: Candidatus Phormidium alkaliphilum
Target Taxon: Verrucomicrobiota members
Metabolites: polysaccharide (CHEBI:18154 · MediaIngredientMech · CMMMech)
Biological Processes:
- polysaccharide catabolic process (GO:0000272 · PathwayMech)
Evidence
-
doi:10.3389/fmicb.2022.780346 - PARTIAL (COMPUTATIONAL)"All four consortium members affiliated with Verrucomicrobiota had 6–38 genes for glycoside hydrolysis and 12–37 genes encoding sulfatases"
Alphaproteobacterial Heterotrophic Carbon Use
PARTIAL - Alphaproteobacterial genomes support heterotrophic niches, and the lower-peptide Rhodobacteraceae MAG58 isotope signal is consistent with cyanobacterial carbon use. Oceanicaulis MAG52 and Roseinatronobacter MAG58 also encode bacteriochlorophyll-associated phototrophic capacity, not demonstrated photosynthetic flux. The study does not establish class-wide vitamin provision, siderophore delivery, nitrogen recycling or reciprocal cyanobacterial benefit; Figure 4 has much weaker peptide coverage for MAG58 than the major heterotrophs.
Source Taxon: Candidatus Phormidium alkaliphilum
Target Taxon: Alphaproteobacteria members
Evidence
-
doi:10.3389/fmicb.2022.780346 - PARTIAL (IN_VITRO)"tight coupling of carbon transfer from cyanobacteria to the heterotrophic populations"
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which genomic niches and reciprocal services operate in this alkaline consortium?
Retain experimental carbon flow and qualified genomic niches. Introductory examples of vitamin/siderophore delivery, nutrient remineralization and ROS protection in other phototroph systems do not demonstrate the removed exact-community services. The nutrient-return to vitamin-production arrow has no supporting experiment. Figure 3 explicitly depicts inference from gene content; Figure 4 supports carbon flow, not compound-resolved flux or a trophic cascade. Bacteroidota remains a genuine member with inferred metabolic niches, not proven nutrient-return function. Stability over years does not mean fixed membership or experimentally established redundancy mediation. Additional niche and MAG-resolved graph coverage remains issue #1699 pending scoped Edison report; no unsupported edge is added to give every taxon connectivity credit.
Attaches to: ecological_interactions#Photosynthetic CO2 Fixation, ecological_interactions#Carbon Transfer to Heterotrophs, ecological_interactions#Proposed Cyanobacterial Polymer Use by Verrucomicrobiota, ecological_interactions#Alphaproteobacterial Heterotrophic Carbon Use
2 evidence item(s)
tight coupling of carbon transfer from cyanobacteria to the heterotrophic populations
Experimental labeling supports carbon flow; full Figure 4 distinguishes the two major heterotrophic populations from lower-peptide populations.
All four consortium members affiliated with Verrucomicrobiota had 6–38 genes for glycoside hydrolysis and 12–37 genes encoding sulfatases
Primary Results assign the hydrolase/sulfatase genomic capacity to these four MAGs, not a demonstrated cross-phylum handoff.
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Alkaline pH | >11 | pH units |
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| Stable Growth Duration | 4 years | years |
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| Light Cycle | 16:8 hours | light:dark hours |
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| Temperature | ~25 | °C |
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| Biomass Productivity | 15.2 ± 1.0 | g/m²/day |
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| Community Robustness Mechanisms | Niche partitioning and functional redundancy | N/A |
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Growth Media
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