TraitMech

TraitMech › OTHER

methyl red test negative

METPO:1005015 · CLASS · SEEDED

A phenotype in which an organism tests negative in the methyl red test.

Trait evidence (3)

  • https://asm.org/getmedia/40946f85-9357-4563-aa8a-994427efa825/Methyl-Red-and-Voges-Proskauer-Test-Protocols.pdf
    A negative MR test is indicated by a yellow color in the culture medium (Fig. 1B), which occurs when less acid is produced (pH is higher) from the fermentation of glucose.

    The ASM protocol PDF defines the negative methyl-red-test readout as a yellow culture after methyl red is added, reflecting less acidification during glucose fermentation.

  • DOI:10.1128/JCM.42.8.3665-3669.2004
    In the ASM Manual of Clinical Microbiology, only 6 of the 18 biochemical tests used in the present investigation are listed for Klebsiella species: indole, MR, VP, LDC, ODC, and malonate

    Hansen et al. evaluated methyl red as a conventional Klebsiella biochemical test; their Table 2 reports K. pneumoniae methyl-red result percentages across CPHL, NRL, and SSI.

  • DOI:10.1128/JCM.42.8.3665-3669.2004
    Variable results were of two types: (i) those in which all three laboratories found a mixture of positive and negative results among the representatives of a species for a specific test (e.g., K. pneumoniae and l-sorbose), suggesting a truly variable reaction, and (ii) those in which one center found most strains to be negative while another found most positive (e.g., K. rhinoscleromatis and MR) or vice versa, suggesting that the results were method dependent.

    The same interlaboratory evaluation found that MR could be method dependent for some Klebsiella species/test combinations, so the K. pneumoniae canonical example is recorded from Table 2 results rather than treated as a species-wide invariant.

Provenance

Identifier source
METPO (2026-06-12)
Definition source
https://asm.org/getmedia/40946f85-9357-4563-aa8a-994427efa825/Methyl-Red-and-Voges-Proskauer-Test-Protocols.pdf

Parent traits (1)

kg-microbe context

No kg-microbe node embedding matched this record in the 2026-04-25 deepwalk.

Canonical examples (1)

Organisms cited as exemplars of this trait. Taxon ids are NCBITaxon and link out to the NCBI record.

Discussions and Knowledge Gaps (1)

Open questions attached to this trait. Seeded by just knowledge-gap-scan and curated; see the corpus-wide index.

Resolve a non-assay parent for negative methyl-red-test phenotypes before narrowing parent_traits below phenotype.

CURATION TODO RESOLVED methyl-red-test-negative-assay-parent-gap · raised by codex · 2026-09-12

Not yet attached to a section of this record — a curator sets attaches_to (e.g. causal_graphs#some_edge) so the gap shows beside the mechanism it concerns.

METPO:1005013 is the seeded superclass of METPO:1005015, but METPO:1005013 defines an assay rather than a broader microbial trait class, so this record is temporarily parented directly to METPO:1000059 phenotype.

Resolution: METPO:1005013 is now represented as the seeded methyl-red-test assay parent, so this assay-outcome phenotype can use its exact source superclass instead of a temporary direct phenotype parent; this resolves the exact METPO assay-parent gap, not the broader non-assay parent question for assay-outcome phenotypes.

Curation history

  1. · SEEDED_FROM_METPO · seed_from_metpo

    imported from data/raw/metpo.owl (CLASS)

  2. · ENRICHED_FROM_LITERATURE · codex

    Added the METPO methyl-red-test-negative phenotype with stable-URL and DOI-backed methyl-red-test evidence after a repository-wide duplicate review covering ignored and hidden files.

  3. · CURATION_REVIEW_REVISION · codex

    Added the Hansen Klebsiella pneumoniae canonical example after local review issue #861 showed Table 2 directly supports a mostly methyl-red-negative Klebsiella pneumoniae result.

  4. · RESOLVED_PARENT_GAP · codex

    Reparented methyl red test negative below the newly curated METPO:1005013 methyl red test assay parent and marked the temporary assay-parent discussion resolved.

  5. · CURATION_REVIEW_REVISION · codex

    Moved the methyl-red parent-gap closure into resolution_note and resolved_date so the original non-assay parent rationale remains visible.