dissimilatory manganese reduction

Deep research

Generated by just research-trait; source: research/traits/metabolism/dissimilatory_manganese_reduction-deep-research-falcon.md

# Curation report: dissimilatory manganese reduction

## Trait record and scope

- **Trait label:** dissimilatory manganese reduction
- **Trait identifier:** `traitmech:000108`
- **Category / kind / status:** METABOLISM / CLASS / REVIEWED
- **Parent:** `traitmech:000039`
- **Synonym:** Mn(IV) reduction

The trait should denote an **anaerobic, energy-conserving respiratory capacity** in which extracellular Mn(IV) oxide is used as the terminal electron acceptor while an organic compound or H₂ supplies electrons, with Mn(II) normally accumulating as the reduced product. Lovley’s operational definition was use of Mn(IV) as an external electron acceptor; Mn(II) is generally the endpoint, although Mn(III) can occur as an intermediate. Growth on the nonfermentable donor acetate coincident with Mn(IV) reduction and proton translocation with lactate/Mn(IV) provide physiological evidence that this can support energy conservation. (lovley1991dissimilatoryfe(iii)and pages 20-21, lovley1991dissimilatoryfe(iii)and pages 2-3)

### Boundaries

**Include** a phenotype when Mn(IV) reduction is linked to anaerobic electron transport and preferably to growth, increased biomass, proton translocation, ATP formation, or a donor/acceptor-dependent growth yield.

**Exclude or represent separately:**

1. **Assimilatory Mn reduction**, where manganese is reduced during incorporation into enzymes, cofactors, or cellular material. Dissimilatory reduction instead produces substantial extracellular Mn(II). (lovley1991dissimilatoryfe(iii)and pages 2-3)
2. **Mn(II) oxidation**, the reverse biogeochemical process.
3. **Incidental or detoxifying reduction** by aerobically grown/resting cells without evidence of energy conservation.
4. **Minor fermentative electron disposal.** Some fermenters transfer less than 5% of substrate reducing equivalents to Fe(III)/Mn(IV), with no demonstrated growth energy from metal reduction. (lovley1991dissimilatoryfe(iii)and pages 2-3)
5. **Indirect abiotic Mn(IV) reduction** by microbially produced Fe(II), sulfide, FeS, pyrite, sulfite, or other reductants. A rise in dissolved Mn alone therefore does not establish direct enzymatic respiration. (lovley1991dissimilatoryfe(iii)and pages 2-3, wunder2024manganesereductionand pages 6-7)
6. **Mn(III)-only respiration** unless the experiment establishes that Mn(III) is an intermediate or relevant Mn(IV)-oxide phase rather than a separate terminal acceptor.

## Candidate graph nodes

### Trait and process nodes

- Dissimilatory manganese reduction — `traitmech:000108`
- Anaerobic respiration — candidate `GO:0009061`
- Extracellular electron transfer — label-only pending ontology review
- Electron-transport-linked energy conservation — label-only
- Proton translocation / proton-motive-force generation — use an appropriate GO term only after confirming the intended granularity
- Organic-matter oxidation and mineralization — label-only at this graph granularity

### Chemicals and minerals

- Mn(IV) oxide / manganese dioxide — terminal electron acceptor; mineral phase should remain label-only unless the experimental form is known
- Birnessite — experimentally supplied Mn oxide; label-only mineral node
- Mn(II) — candidate `CHEBI:29035` (manganese(2+)); verify whether the graph intends the ion or total dissolved Mn
- Mn(III) — possible intermediate; do not make obligatory
- Acetate — candidate `CHEBI:30089`
- Lactate — stereochemistry varies; ground only when reported
- Formate — candidate `CHEBI:15740`
- Hydrogen — candidate `CHEBI:18276`
- Elemental sulfur, thiosulfate, sulfide — potential donors in some systems, but negative or inconclusive in the 2024 Potter Cove experiment
- Menaquinone-7 / menaquinol-7 and ubiquinone-8 — membrane electron carriers in *Shewanella*; exact CHEBI mappings should be registry-validated
- Flavins/FMN — extracellular shuttles or cytochrome-associated cofactors; not universally required
- Fe(II), FeS, pyrite and sulfide — confounders capable of abiotic Mn-oxide reduction
- AQDS — experimental electron shuttle; not intrinsic to the core trait

### Genes, proteins, and complexes

**Conservative *Shewanella* module:**

- NADH dehydrogenases, lactate dehydrogenases, formate dehydrogenases — donor oxidation and quinone reduction
- **CymA** — inner/cytoplasmic-membrane tetraheme c-type cytochrome; oxidizes membrane quinols and distributes electrons
- Periplasmic carriers, including **STC**, **FccA**, and **ScyA** — candidate intermediate carriers, but redundancy and Mn specificity remain unresolved
- **MtrA** — periplasm-facing decaheme cytochrome

Showing the first 60 of 199 lines of findings; the linked file also carries the run's front matter and the prompt it was given — read the full report.