Alaska Tundra Permafrost Iron-Redox Community

Community ID CommunityMech:000262

Ecological State PERTURBED

Environment wet sedge tundra permafrost soil
ENVO:00002179

A northern Alaska wet sedge tundra microbial community studied across the permafrost thaw gradient, where iron-cycling Gammaproteobacteria - the heterotrophic Fe(III)-reducing Rhodoferax sp. and the chemoautotrophic Fe(II)-oxidizing Gallionella sp. - become numerically dominant during extended anaerobic thaw of transition-zone and permafrost soils. Functional gene abundance shows that Fe(III) reduction and Fe(II) oxidation increase in lockstep with benzoate degradation and pyruvate metabolism, supporting a carbon-cycling model in which acetate and benzoate are oxidized to CO2 coupled to Fe(III) reduction. Concurrent decreases in CH4-metabolism gene abundance suggest that dissimilatory Fe(III) reduction competitively suppresses acetoclastic methanogenesis under the reducing thaw conditions examined.

Taxonomy

Taxon	Ontology ID	Functional Roles	Abundance
heterotrophic Fe(III)-reducing Rhodoferax sp.	NCBITaxon:28065	PRIMARY_DEGRADER CROSS_FEEDER	DOMINANT
PMID:37996661 - SUPPORT (COMPUTATIONAL) "Following extended thaw, we found that iron (Fe)-cycling Gammaproteobacteria, specifically the heterotrophic Fe(III)-reducing Rhodoferax sp. and chemoautotrophic Fe(II)-oxidizing Gallionella sp., increased by 3-5 orders of magnitude in absolute abundance"
chemoautotrophic Fe(II)-oxidizing Gallionella sp.	NCBITaxon:96	PRIMARY_PRODUCER	DOMINANT
PMID:37996661 - SUPPORT (COMPUTATIONAL) "chemoautotrophic Fe(II)-oxidizing Gallionella sp., increased by 3-5 orders of magnitude in absolute abundance within the transition-zone and permafrost microbiomes, accounting for 65% of community abundance"
wet sedge tundra methanogens	NCBITaxon:224756	SECONDARY_FERMENTER	N/A
PMID:37996661 - SUPPORT (COMPUTATIONAL) "Gene abundance for CH4 metabolism decreased following extended thaw, suggesting dissimilatory Fe(III) reduction suppresses acetoclastic methanogenesis"

Ecological Interactions

Taxon

Cross-feeding

Mutualism

Syntrophy

Competition

Commensalism

Niche partitioning

Colonization facilitation

Strain competition

Predation

Fe(III) Reduction Coupled to Organic Acid Oxidation

SYNTROPHY

Source Taxon: heterotrophic Fe(III)-reducing Rhodoferax sp.

Metabolites: acetate (CHEBI:30089), benzoate (CHEBI:16150), iron(3+) (CHEBI:29034), iron(2+) (CHEBI:29033), carbon dioxide (CHEBI:16526)

Biological Processes:

iron ion transport (GO:0006826)
oxidation-reduction process (GO:0055114)

Evidence

PMID:37996661 - SUPPORT (COMPUTATIONAL)

"the abundance of genes for Fe(III) reduction (e.g., MtrE) and Fe(II) oxidation (e.g., Cyc1) increased concurrently with genes for benzoate degradation and pyruvate metabolism, in which pyruvate is used to generate acetate that can be oxidized, along with benzoate, to CO2 when coupled with Fe(III) reduction"

Fe(III) Reduction Suppresses Acetoclastic Methanogenesis

COMPETITION

Source Taxon: heterotrophic Fe(III)-reducing Rhodoferax sp.

Target Taxon: wet sedge tundra methanogens

Metabolites: acetate (CHEBI:30089), methane (CHEBI:16183)

Biological Processes:

methane biosynthetic process (GO:0015948)

Evidence

PMID:37996661 - SUPPORT (COMPUTATIONAL)

"dissimilatory Fe(III) reduction suppresses acetoclastic methanogenesis under reducing conditions"

Fe(II) Oxidation by Chemoautotrophic Gallionella

CROSS_FEEDING

Source Taxon: chemoautotrophic Fe(II)-oxidizing Gallionella sp.

Target Taxon: heterotrophic Fe(III)-reducing Rhodoferax sp.

Metabolites: iron(2+) (CHEBI:29033), iron(3+) (CHEBI:29034)

Biological Processes:

iron ion transport (GO:0006826)

Evidence

PMID:37996661 - PARTIAL (COMPUTATIONAL)

"the abundance of genes for Fe(III) reduction (e.g., MtrE) and Fe(II) oxidation (e.g., Cyc1) increased concurrently"

Environmental Factors

Factor	Value	Unit
Anaerobic thaw incubation	30 days at 4 deg C under reducing conditions	N/A
PMID:37996661 - SUPPORT (IN_VITRO) "Organic soils from the tundra active-layer (0-50 cm), transition-zone (50-70 cm), and permafrost (70+ cm) depths were incubated under reducing conditions at 4 °C for 30 days to mimic an extended thaw duration"
Permafrost depth gradient	active-layer / transition-zone / permafrost	N/A
PMID:37996661 - SUPPORT (IN_VITRO) "relative and absolute changes in microbiome composition and functional gene abundance during thaw incubations of wet sedge tundra collected from northern Alaska, USA"