Silver element Critical Material
Silver (Ag). The element identity is distinct from the silver(I) salts and precipitates used in the laboratory experiment below. The dated US designation concerns the silver mineral commodity; it is mapped here to its elemental identity, not inherited by every silver-bearing material.
Identifiers & Classification
| System | Identifier | Label |
|---|---|---|
| CHEBI |
CHEBI:30512
|
silver atom |
Criticality Designations
| Jurisdiction | List Name | Edition / Document | Classification | Source |
|---|---|---|---|---|
| United States of America | U.S. Department of the Interior Final List of Critical Minerals | 2025 (published November 7, 2025; 90 FR 50494-50497) | critical |
usgs_2025
|
Microbial & Biochemical Mechanisms (1)
Anaerobic culture-associated formation of elemental silver
redox transformation
Microbial
Associated Organisms:
Shewanella oneidensis MR-1 (NCBITaxon:211586)
Growing Shewanella oneidensis MR-1 cultures transformed Ag(I)-bearing material to precipitates containing XRD-identified elemental Ag(0). This laboratory observation does not establish an isolated-product yield, complete conversion, or industrial recovery process.
Experimental Context & Analytical Limits:
Defined chloride/phosphate-containing medium with 100 mM lactate and 20 mM fumarate, adjusted to pH 7.6 before sterilization; anaerobic incubation at 30 degrees C in the dark. General exposure methods add AgNO3 at nominal 1-400 micromolar Ag(I), with 10 mL inoculum added to 80 mL medium, and state six biological replicates. The separate XRD protocol specifies 1 L medium with 100 micromolar AgCl, no agitation, and 24 h incubation. This difference in stated starting salt is retained, not resolved by treating all added Ag as dissolved AgNO3. XRD samples were centrifuged, water-washed, and dried anaerobically.
Defined chloride/phosphate-containing medium with 100 mM lactate and 20 mM fumarate, adjusted to pH 7.6 before sterilization; anaerobic incubation at 30 degrees C in the dark. General exposure methods add AgNO3 at nominal 1-400 micromolar Ag(I), with 10 mL inoculum added to 80 mL medium, and state six biological replicates. The separate XRD protocol specifies 1 L medium with 100 micromolar AgCl, no agitation, and 24 h incubation. This difference in stated starting salt is retained, not resolved by treating all added Ag as dissolved AgNO3. XRD samples were centrifuged, water-washed, and dried anaerobically.
Curated Evidence Points:
Support
Source:
wang_2010
Methods (XRD analysis), Results (Analysis of silver precipitates), and Figure 3 compare AgCl/Ag3PO4-containing precipitates without cells with Ag(0) diffraction after culture incubation. No-cell media lacked the culture-associated color change. Figure 4 shows cell-associated electron-dense particles after Ag exposure, absent from the no-Ag control; microscopy alone does not assign the oxidation state of each particle.
Partial
Source:
wang_2010
Results and Figure 2 show dose-dependent limits: growth was delayed at nominal 100 micromolar Ag(I) and absent at 400 micromolar. Abiotic precipitation means nominal added Ag(I) differs from dissolved exposure. The abstract's statement that 100 micromolar reduced doubling time conflicts with the Results, which report an increase from about 7.5 to 24 h. Proposed roles for cytochromes or flavins in the Discussion were not tested causally in this experiment; neither solution depletion nor product mass balance was established for the inoculated cultures.
Sources & References
-
chebi_silver: ChEBI:30512 - silver atom (Ag; net charge zero)
https://www.ebi.ac.uk/chebi/CHEBI:30512 (accessed 2026-10-11) -
usgs_2025: U.S. Geological Survey (2025). Final 2025 List of Critical Minerals. Federal Register 90 FR 50494-50497, November 7, 2025; silver commodity entry on page 50497.
https://www.govinfo.gov/content/pkg/FR-2025-11-07/html/2025-19813.htm (accessed 2026-10-11) -
wang_2010: Wang et al. (2010). Impact of Silver(I) on the Metabolism of Shewanella oneidensis. Journal of Bacteriology 192(4), 1143-1150. DOI 10.1128/JB.01277-09; published online December 11, 2009.
https://pmc.ncbi.nlm.nih.gov/articles/PMC2812967/ (accessed 2026-10-11) -
ncbi_mr1: NCBI Taxonomy: Shewanella oneidensis MR-1 (Taxonomy ID 211586; no rank)
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=211586&mode=Info (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T04:20:51Z |
Codex (GPT-6; Codex) | create | Created silver identity, dated US criticality and an MR-1 laboratory transformation mechanism from verified authority pages and primary methods, results and figures. Preserved starting-salt ambiguity, abiotic precipitation, dose limitation and inferred molecular cause; attached the separate canonical CREATE session before review. |
Record source: data/records/silver.yaml