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Manganite mineral

Manganite is the manganese(III) oxide hydroxide mineral MnO(OH), listed as grandfathered in the September 2026 IMA-CNMNC list. The year 1826 is its historical date, not an IMA approval accession. It is distinct from elemental manganese, manganese ore, the MnO2 minerals pyrolusite and ramsdellite, and other MnOOH polymorphs. The experiment below used laboratory-prepared material assigned to manganite by the source, not natural ore or a certified phase-pure mineral reference. No criticality designation is inherited from manganese.

Microbial & Biochemical Mechanisms (1)

Anaerobic MR-4-associated reductive dissolution of synthetic manganite

redox transformation Microbial

Associated Organisms: Shewanella sp. MR-4 (NCBITaxon:60480)

Living MR-4 cultures increased filtered dissolved manganese from source-assigned synthetic manganite in anaerobic laboratory incubations. The authors interpret this as Mn(III)-to-Mn(II) reductive dissolution. Uninoculated, heat-killed, oxygen-exposed and dialysis-separated comparisons strongly limited release under the tested conditions. This supports a culture-associated process with contact and metabolic dependencies in this assay, not a universal requirement for direct electron transfer, an identified reductase, pure-phase mass balance, isolated manganese product or industrial recovery.

Experimental Context & Analytical Limits:
Larsen1998 calls the culture Shewanella putrefaciens MR-4; the current NCBI name is Shewanella sp. MR-4, not an authenticated sequence match to the historical laboratory stock. Cells were serially acclimated, centrifuged and resuspended in defined M1 medium containing 30 mM lactate without the casamino acids used during pregrowth. Standard experiments used 250 mL open flasks inside a 10% H2/90% N2 anaerobic chamber at reported 27 degrees C, medium adjusted to pH 7.4, nominal 200 micromol/L MnOOH and 5 x 10^6 cells/mL unless varied. The H2 atmosphere means the no-added-carbon arm is not an electron-donor-free system. Manganite was prepared from MnSO4, H2O2 and NH3, heated at 95 degrees C for six hours, washed hot and cold and stored frozen. The paper gives needle morphology and a synthesis recipe but no batch-specific diffraction refinement, quantified phase purity or measured composition. Separate pH and temperature arms used sealed 50 mL serum bottles and only two sampling times.
Curated Evidence Points:
Figures 1-3 and Results on pages 1566-1567 show increasing filtered manganese with active cultures and much smaller release in no-cell, killed-cell, oxygen, CCCP and no-contact comparisons. Figure 3 groups several negative controls in one symbol series; the no-added- carbon arm still releases manganese before its rate decreases. The dialysis experiment supports a contact dependency under its protocol, not exclusion of every diffusible mediator in other systems. Table 1 shows strong inhibition by CCCP and HgCl2, but weak HQNO inhibition and zero reported cyanide inhibition; not all tested inhibitors suppress release. No enzyme, gene or electron-transfer pathway was experimentally identified.
Methods on pages 1565-1566 measure 0.2 micrometre-filtered, acidified samples by flame atomic absorption. This is dissolved-element quantification interpreted as Mn(II), not direct oxidation-state speciation. Three samples per flask and repeated instrument readings measure subsampling/analytical variability; they do not establish three independent culture replicates. The paper reports a repeated standard treatment but Figure 1's duplicate series is labelled 100 micromol/L, whereas the methods' repeated treatment is 200 micromol/L. Complete eventual reduction is stated with data not shown. No complete manganese/product mass balance or isolated recovery yield is adopted.
Table 1 on page 1568 records inoculated versus no-cell dissolved manganese means of 101.3 versus 103.1 micromol/L at pH 4 and 39.4 versus 44.0 micromol/L at pH 5. These acidic arms do not demonstrate a positive microbial increment; acid-driven release predominates. At pH 7.4, means are 12.2 versus 1.2 micromol/L. These selected table means retain their units and arm identities, without being treated as recovery percentages or independent biological replicates. The table omits net-reduction entries for the two acidic arms rather than reporting negative values.
The abstract calls the optimum pH 7.0 and 26 degrees C; methods list pH 7.4 and temperatures 4, 27, 37 and 44 degrees C; Table 1 labels the largest measured net temperature response 26 degrees C; the discussion instead says around 35 degrees C. No precise optimal temperature or pH is asserted. Figure 2 specifies a 100-fold cell range, while the results text says 300-fold and gives slightly different sampling times. These discrepancies are not silently reconciled into a kinetic model.
Figure 4 shows manganite-associated manganese release intermediate between the tested birnessite and pyrolusite preparations. The estimated manganite area of 0.9-2.5 m2/g is microscopy-derived, not a direct BET measurement. Different surface areas, morphology, chemistry and crystallinity confound an intrinsic mineral ranking; the authors explicitly call for better area measurements. This comparison does not duplicate a new birnessite or pyrolusite owner.
Figures 5-9 compare uninoculated particles with colonized material using wet fixed ESEM and dehydrated, gold-coated SEM. Cell-associated coatings and close contact support biofilm association, but their composition and causal role in reduction remain undetermined. Polysaccharide chemistry is a proposed interpretation. Figure 8 is labelled approximately 75% reduced in its caption but described as greater than 90% in the results; neither is used as a quantified recovery endpoint. Sample washing, fixation and dehydration limit inference about native hydrated surface architecture.
Context_only Source: ncbi_mr4
NCBI 60480 resolves the current strain-labelled name and its placement under unclassified Shewanella. It does not turn the historical S. putrefaciens designation into a verified modern species assignment or establish this phenotype for all Shewanella.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Manganite row, PDF page 134; introductory status/date definitions and terms.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-14)
  2. manganite_handbook: Mineralogical Society of America, Handbook of Mineralogy. Manganite, one-page entry, Mineral Data Publishing 2001-2005 version 1; mineral identity, monoclinic structure, composition and polymorphism.
    https://handbookofmineralogy.org/pdfs/manganite.pdf (accessed 2026-10-14)
  3. larsen1998: Larsen, Little, Nealson, Ray, Stone and Tian (1998). Manganite reduction by Shewanella putrefaciens MR-4. American Mineralogist 83:1564-1572. Complete nine-page original, methods, Figures 1-9 and Table 1.
    https://doi.org/10.2138/am-1998-11-1244 (accessed 2026-10-14)
  4. larsen1998_original: RRUFF document archive. Complete American Mineralogist 83:1564-1572 original PDF of Larsen et al. (1998), AM83_1564.pdf.
    https://www.rruff.net/doclib/am/vol83/AM83_1564.pdf (accessed 2026-10-14)
  5. ncbi_mr4: NCBI Taxonomy 60480, current name Shewanella sp. MR-4, a strain-labelled unclassified Shewanella taxon with species rank; Datasets response.
    https://api.ncbi.nlm.nih.gov/datasets/v2/taxonomy/taxon/60480/dataset_report (accessed 2026-10-14)

Curation History

Timestamp Curator Action Summary
2026-10-14T06:24:24Z codex (GPT-6; Codex) CREATE Add mineral identity and source-qualified synthetic manganite reduction by MR-4, retaining controls, source contradictions and scale limits.

Record source: data/records/manganite.yaml