Cesium element Critical Material
Cesium (caesium; Cs), represented as an element distinct from Cs(I) salts, radioactive isotopes, pollucite mineral and cesium-bearing commodities or wastes. A laboratory study measured Cs retained by washed Bifidobacterium adolescentis biomass after growth in non-radioactive cesium chloride. The US 2025 critical-mineral designation names the cesium commodity; it does not designate every cesium compound or imply deployment of a microbial recovery process.
Identifiers & Classification
| System | Identifier | Label |
|---|---|---|
| CHEBI |
CHEBI:30514
|
caesium 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)
Cesium retention by washed Bifidobacterium adolescentis JCM 1275 biomass
other
Microbial
Associated Organisms:
Bifidobacterium adolescentis (NCBITaxon:1680)
Cultured Bifidobacterium adolescentis JCM 1275 retained Cs measurable in washed, digested cell pellets. Cs remained associated with biomass after a subsequent Sr exposure, but the retained amount fell. The study supports laboratory biomass association; intracellular polyphosphate trapping and contributions from surface sorption remain proposed explanations. It does not establish a Cs redox reaction, selective recovery from ore or waste, an isolated cesium product, or efficacy in an animal or human digestive tract.
Experimental Context & Analytical Limits:
Endo et al., Culture conditions and Determination of Cs contained in bacterial cells: two precultures with 1% volume/volume inoculum preceded static incubation for 24 h at 37 degrees Celsius with 50 mM non-radioactive Cs supplied as CsCl. The bifidobacterial medium contained 10 g/L casein peptone, 5 g/L beef extract, 5 g/L yeast extract, 10 g/L glucose, 3 g/L K2HPO4 and 1 mL/L Tween 80; sodium ascorbate (1% weight/volume) and L-cysteine hydrochloride (0.05% weight/volume) were added after autoclaving. Culture pH, controlled gas atmosphere and a drying protocol for the dry-mass denominator are not specified in these methods. Pellets were collected at 6000 x g for 3 min and washed twice by resuspension in distilled water and centrifugation, then digested in nitric acid with hydrogen peroxide for ICP-MS. A separate mapping experiment used 100 mM Cs, not the 50 mM capacity condition. In the sequential arm, cells from 2 mL culture were washed and suspended in 2 mL of 1 mM Bis-Tris, pH 6.8, with 1 mM non-radioactive SrCl2, incubated for 3 h at 37 degrees Celsius with 200 strokes/min (25 mm stroke), collected, washed and digested. This was sequential Cs loading then Sr exposure, not concurrent extraction from a mixed Cs/Sr feed.
Endo et al., Culture conditions and Determination of Cs contained in bacterial cells: two precultures with 1% volume/volume inoculum preceded static incubation for 24 h at 37 degrees Celsius with 50 mM non-radioactive Cs supplied as CsCl. The bifidobacterial medium contained 10 g/L casein peptone, 5 g/L beef extract, 5 g/L yeast extract, 10 g/L glucose, 3 g/L K2HPO4 and 1 mL/L Tween 80; sodium ascorbate (1% weight/volume) and L-cysteine hydrochloride (0.05% weight/volume) were added after autoclaving. Culture pH, controlled gas atmosphere and a drying protocol for the dry-mass denominator are not specified in these methods. Pellets were collected at 6000 x g for 3 min and washed twice by resuspension in distilled water and centrifugation, then digested in nitric acid with hydrogen peroxide for ICP-MS. A separate mapping experiment used 100 mM Cs, not the 50 mM capacity condition. In the sequential arm, cells from 2 mL culture were washed and suspended in 2 mL of 1 mM Bis-Tris, pH 6.8, with 1 mM non-radioactive SrCl2, incubated for 3 h at 37 degrees Celsius with 200 strokes/min (25 mm stroke), collected, washed and digested. This was sequential Cs loading then Sr exposure, not concurrent extraction from a mixed Cs/Sr feed.
Curated Evidence Points:
Support
Source:
endo_2024
Results, Cs removal capacity, and Figure 4a report 70.5 mg Cs/g dry cells for JCM 1275 after the 50 mM Cs culture. After the sequential Sr step, the text reports 55.7 mg Cs/g dry cells and 8.1 mg Sr/g dry cells (Figure 4), with a 21% decline in retained Cs. These are biomass-normalized elemental contents, not feed-removal percentages. Figure 4 describes standard-error bars with n=3 but does not distinguish biological from technical replication; exact numerical error values are not tabulated.
Partial
Source:
endo_2024
Figure 1 shows localized Cs and P signals, with K mapped in the same preparations, after the distinct 100 mM exposure. The authors propose intracellular polyphosphate binding, but the study does not chemically identify polyphosphate, resolve all signals as intracellular, or use a metabolic inhibitor, mutant or killed-cell comparison for Cs. Surface association and multiple retention modes remain possible; process other avoids selecting a demonstrated uptake or sorption pathway.
Partial
Source:
endo_2024
Figure 3 contrasts immediate Cs-loaded biomass with biomass subsequently incubated in Sr buffer. A matched post-loading, Sr-free buffer-incubation arm is not described, so the Cs decrease cannot uniquely establish Sr-driven ion exchange rather than release during handling or incubation. No whole-feed Cs mass balance, cell-free precipitation comparison or isolated product yield is reported. Figure 2f includes a zero-Cs growth control and shows strong growth inhibition at 100-200 mM; that control is not a mechanistic Cs-retention control.
Partial
Source:
endo_2024
Growth inhibition discussion explicitly states that 50 mM Cs and the medium composition do not represent practical gastrointestinal conditions. Non-radioactive reagents were used. The paper proposes future in vivo work; radionuclide decorporation, medical efficacy, field remediation and industrial recovery are not demonstrated.
Sources & References
-
endo_2024: Endo, Karasawa and Aoyagi (2024). Simultaneous removal of caesium and strontium using different removal mechanisms of probiotic bacteria. Scientific Reports 14, 7630. DOI 10.1038/s41598-024-57678-8; PMID 38561437; PMC10984957.
https://doi.org/10.1038/s41598-024-57678-8 (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; Cesium row in the final commodity table. The adjacent No describes byproduct/co-product occurrence, not criticality.
https://www.govinfo.gov/content/pkg/FR-2025-11-07/html/2025-19813.htm (accessed 2026-10-11) -
chebi_cesium: ChEBI:30514 - caesium atom; Cs, net charge zero. Cesium is a listed synonym.
https://www.ebi.ac.uk/chebi/CHEBI:30514 (accessed 2026-10-11) -
ncbi_adolescentis: NCBI Taxonomy 1680 - Bifidobacterium adolescentis, species. This identifier is species-level; the experimental strain is JCM 1275.
https://api.ncbi.nlm.nih.gov/datasets/v2/taxonomy/taxon/1680/dataset_report (accessed 2026-10-11) -
jcm_1275: RIKEN JCM Catalogue: Bifidobacterium adolescentis JCM 1275T, equivalent to ATCC 15703 and DSM 20083. Strain provenance; not independent assay evidence.
https://www.jcm.riken.jp/cgi-bin/jcm/jcm_number?JCM=1275 (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T06:51:22.812641Z |
Codex (GPT-6; Codex) | create_record | Created elemental cesium with dated US criticality and primary evidence for washed JCM 1275 biomass retention; retained sequential-design, release, mechanism and deployment limits. |
Record source: data/records/cesium.yaml