Samarium element Critical Material
The element Sm, distinct from Sm(III), samarium nitrate, mineral species, alloys and waste streams. The dated US designation concerns the named samarium mineral commodity, without assigning that designation to every Sm-bearing material. The mechanism concerns laboratory culture-associated depletion from a synthetic solution and qualitative biomass enrichment, not a purified samarium product or industrial process.
Identifiers & Classification
| System | Identifier | Label |
|---|---|---|
| CHEBI |
CHEBI:33374
|
samarium atom |
Criticality Designations
| Jurisdiction | List Name | Edition / Document | Classification | Source |
|---|---|---|---|---|
| United States of America | USGS Final List of Critical Minerals | 2025; Federal Register 90:50494-50497, 7 November 2025 | critical |
usgs2025
|
Microbial & Biochemical Mechanisms (1)
Samarium sorption associated with Anabaena cylindrica SAG 1403-2 cultures
biosorption
Microbial
Associated Organisms:
Anabaena cylindrica PCC 7122 (NCBITaxon:272123)
Anabaena cylindrica cultures exposed to samarium nitrate showed a decrease in supernatant Sm and characteristic Sm signals in washed biomass. This supports a biosorption interpretation under the assay conditions. It does not resolve passive surface binding versus intracellular uptake, demonstrate Sm(III) reduction, establish selectivity among mixed rare earths or quantify a recovered product.
Experimental Context & Analytical Limits:
The article names SAG 1403.2, represented by the SAG catalogue as SAG 1403-2. NCBI taxon 272123 uses the preferred name A. cylindrica PCC 7122 and explicitly includes SAG 1403-2 as a co-identical strain; this does not mean a separately obtained PCC culture was assayed. The catalogue currently lists an axenic culture, but the article does not report a contemporaneous axenity test. Cultures grew in 150 mL modified Bold's Basal Medium in 250 mL flasks, nitrate reduced to 50%, initial medium pH 6.8, reported culture pH 7.3, 22 degrees C, orbital shaking and a 12 h day/night cycle (4200 K light). A nutrient-medium assay used 0.139 mM Sm supplied as Sm(NO3)3·6H2O; an untreated culture half served as a biomass reference. Initial biomass concentration, biological replicate count and a matched incubated biomass-free control are not specified in the inspected main article or supplement. The initial concentration reference was diluted stock without biomass. Two-mL samples were centrifuged at 14000 rpm for 15 min, with stated timing uncertainty of +/- 10 min. Supernatants were filtered through 0.45 micrometre filters, acidified, frozen and measured by ICP-MS; this gives elemental Sm, not an independent oxidation-state measurement. Washed biomass was dried for qualitative LIBS. Color and optical microscopy were used to judge viability; no quantitative viable count or killed-cell comparison was reported. No real-waste extraction, isolated-product yield or industrial deployment was demonstrated.
The article names SAG 1403.2, represented by the SAG catalogue as SAG 1403-2. NCBI taxon 272123 uses the preferred name A. cylindrica PCC 7122 and explicitly includes SAG 1403-2 as a co-identical strain; this does not mean a separately obtained PCC culture was assayed. The catalogue currently lists an axenic culture, but the article does not report a contemporaneous axenity test. Cultures grew in 150 mL modified Bold's Basal Medium in 250 mL flasks, nitrate reduced to 50%, initial medium pH 6.8, reported culture pH 7.3, 22 degrees C, orbital shaking and a 12 h day/night cycle (4200 K light). A nutrient-medium assay used 0.139 mM Sm supplied as Sm(NO3)3·6H2O; an untreated culture half served as a biomass reference. Initial biomass concentration, biological replicate count and a matched incubated biomass-free control are not specified in the inspected main article or supplement. The initial concentration reference was diluted stock without biomass. Two-mL samples were centrifuged at 14000 rpm for 15 min, with stated timing uncertainty of +/- 10 min. Supernatants were filtered through 0.45 micrometre filters, acidified, frozen and measured by ICP-MS; this gives elemental Sm, not an independent oxidation-state measurement. Washed biomass was dried for qualitative LIBS. Color and optical microscopy were used to judge viability; no quantitative viable count or killed-cell comparison was reported. No real-waste extraction, isolated-product yield or industrial deployment was demonstrated.
Curated Evidence Points:
Support
Source:
fischer2019_esi
Table S3 and Figure S3 (page S4) report an initial 0.139 mmol/L Sm reference, 1.52E-3 mmol/L at 18 min, 6.95E-4 at 53 min, 9.42E-5 at 708 min and 1.06E-4 mmol/L at 1488 min. The first decrease is about 98.9%, calculated from the reported initial reference. The main Results describes this approximately as 20 min and less than 1% remaining, but the tabulated values imply about 1.09% remaining; the exact table values are retained. Later very low values are not zero, and their small increase does not establish significant release without a defined statistical analysis. The error column is labelled RSD in mmol/L without its statistical basis or replicate count being explained.
Support
Source:
fischer2019
Experimental, Results, ICP-MS and LIBS, Figure 1 and Figure 4 describe Sm depletion and characteristic Sm emission peaks in biomass after 200 h compared with samarium nitrate and untreated-biomass references. LIBS was explicitly qualitative, so peak intensity does not provide an absolute or relative Sm loading or a mass balance. The reported enrichment concerns this separate Sm assay with A. cylindrica, not the Eu experiment with SAG 12.82.
Partial
Source:
fischer2019
Discussion states that Sm particle formation was not proven in the 2019 series. No exact Sm product phase, reduction mechanism or intracellular localization is assigned here. That study-specific limitation is not a claim that later studies cannot observe Sm particles. Visual absence of bulk precipitation and apparently viable cultures do not replace an incubated abiotic control or establish an exclusively active transport mechanism. Subsequent Sm harvesting and selective separation remain unmeasured in this assay.
Sources & References
-
chebi_samarium: ChEBI CHEBI:33374 - samarium atom; formula Sm, net charge 0
https://www.ebi.ac.uk/chebi/CHEBI:33374 (accessed 2026-10-11) -
usgs2025: USGS (2025). Final 2025 List of Critical Minerals. Federal Register 90:50494-50497, document 2025-19813; samarium row on page 50497.
https://www.govinfo.gov/content/pkg/FR-2025-11-07/html/2025-19813.htm (accessed 2026-10-11) -
fischer2019: Fischer et al. (2019). Cyanobacterial promoted enrichment of rare earth elements europium, samarium and neodymium and intracellular europium particle formation. RSC Advances 9:32581-32593; Experimental, Results, Discussion and Figures 1-9.
https://doi.org/10.1039/C9RA06570A (accessed 2026-10-11) -
fischer2019_esi: Fischer et al. (2019), electronic supplementary information, RA-009-C9RA06570A-s001.pdf; pages S1-S5, Tables S1-S4 and Figures S1-S4. Complete PDF entry recovered with matching CRC32 from the incomplete EuropePMC ZIP download.
https://www.ebi.ac.uk/europepmc/webservices/rest/PMC9073238/supplementaryFiles (accessed 2026-10-11) -
sag_1403_2: SAG culture catalogue, strain 1403-2, Anabaena cylindrica; strain relatives and culture identity
https://sagdb.uni-goettingen.de/detailedList.php?str_number=1403-2 (accessed 2026-10-11) -
ncbi_cylindrica: NCBI Taxonomy 272123 - Anabaena cylindrica PCC 7122; no-rank node explicitly listing SAG 1403-2 as a co-identical strain
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=272123 (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T06:02:59Z |
Codex (GPT-6; Codex) | CREATE | Added verified elemental samarium identity, dated US2025 designation and qualified cyanobacterial sorption evidence; preserved primary-source inconsistencies, analytical limits and laboratory scope. Scientific review is separate. |
Record source: data/records/samarium.yaml