A root-associated rhizosphere microbial community in which drought stress drives reproducible enrichment of bacterial lineages whose iron transport and metabolism functionalities are overrepresented. Genome-resolved metagenomics and comparative genomics show carbohydrate and secondary- metabolite transport functions also dominate drought-enriched taxa. Time- series root RNA-Seq data show that root iron homeostasis is impacted by drought, and loss of a plant phytosiderophore iron transporter increases Actinobacteria abundance. Exogenous iron application disrupts the drought- induced Actinobacteria enrichment and removes their host phenotype improvement, implicating iron metabolism as a microbiome-drought axis.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| drought-enriched rhizosphere Actinobacteria — ontology label: Actinomycetota | NCBITaxon:201174 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
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N/A |
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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.
Drought-Associated Genomic Transport Capacity
Field sorghum rhizosphere metagenomes associate drought enrichment with carbohydrate, secondary-metabolite and iron transport/metabolism gene capacity. Ten of fifteen recovered Actinobacterial MAGs were drought-enriched; five were not. This is genomic potential, not microbial expression, iron flux or a demonstrated fitness effect of the genes. The canonical phylum participant is a partial grouping, not a universal responder or complete microbiome roster.
Participating Taxa: drought-enriched rhizosphere Actinobacteria
Metabolites: iron (CHEBI:24875 · MediaIngredientMech · CMMMech)
Biological Processes:
- iron ion transport (GO:0006826 · PathwayMech)
- carbohydrate transport (GO:0008643 · PathwayMech)
Evidence
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PMID:34050180 - SUPPORT (COMPUTATIONAL)"bacterial iron transport and metabolism functionality is highly correlated with drought enrichment"
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PMID:34050180 - SUPPORT (COMPUTATIONAL)"carbohydrate and secondary metabolite transport functionalities are overrepresented within drought-enriched taxa"
Maize TOM1 Loss and Relative Actinobacteria Enrichment
In a separate maize growth-chamber experiment using field-site soil, loss of TOM1, an exporter of the phytosiderophore mugineic acid, increased relative rhizosphere Actinobacteria under watered controls. The genotype difference was not significant under drought. This host perturbation supports iron-homeostasis involvement but does not establish absolute phylum growth, a sorghum knockout effect or causal selection of the field MAG gene repertoire.
Participating Taxa: drought-enriched rhizosphere Actinobacteria
Metabolites: phytosiderophore (CHEBI:38155 · MediaIngredientMech · CMMMech), iron (CHEBI:24875 · MediaIngredientMech · CMMMech)
Evidence
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PMID:34050180 - SUPPORT (IN_VIVO)"loss of a plant phytosiderophore iron transporter impacts microbial community composition"
Iron Amendment Suppresses the Sc1 Drought Response
Separate gnotobiotic sorghum assays inoculated either Streptomyces coelicolor Sc1 or Pseudomonas syringae Ps1, not their coculture or the field microbiome. Fe3+-EDTA amendment removed the significant drought-versus-control abundance contrast and Sc1-associated fresh-root-biomass benefit. This supports an iron-sensitive Sc1 response, not suppression of every actinobacterium or causal alteration of the field genomic repertoire. The retained phylum participant is only a broader taxonomic grouping for Sc1.
Participating Taxa: drought-enriched rhizosphere Actinobacteria
Metabolites: iron (CHEBI:24875 · MediaIngredientMech · CMMMech)
Evidence
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PMID:34050180 - PARTIAL (IN_VIVO)"exogenous application of iron disrupts the drought-induced enrichment of Actinobacteria, as well as their improvement in host phenotype during drought stress"
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which microbial iron-acquisition functions mediate enrichment in the field community?
Field genomic association, maize TOM1 perturbation and single-isolate sorghum iron amendment are different experiments. The removed arrows did not establish selection of field transport genes by either intervention. Host siderophore export, microbial iron uptake and absolute taxon fitness require exact-system measurements and selective perturbations. Do not import separate chamber media into the field record; existing #647 documents this boundary. Non-graph role and pooled-assay wording remain under #1413.
Attaches to: ecological_interactions#Drought-Associated Genomic Transport Capacity, ecological_interactions#Maize TOM1 Loss and Relative Actinobacteria Enrichment, ecological_interactions#Iron Amendment Suppresses the Sc1 Drought Response
External Resources
| Name | Repository | Resource ID |
|---|---|---|
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Primary publication for the drought rhizosphere iron community
PubMed record for the Xu et al. 2021 Nature Communications paper on iron metabolism in drought-induced rhizosphere microbiome dynamics. |
OTHER | PMID:34050180 |
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DOI landing page
DOI link to the Nature Communications paper. |
OTHER | doi:10.1038/s41467-021-23553-7 |
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Drought stress | drought versus well-watered conditions | N/A |
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| Plant phytosiderophore transporter genotype | phytosiderophore-transporter mutant versus wild type | N/A |
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| Iron amendment | exogenous iron application | N/A |
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