TraitMech

TraitMech › MORPHOLOGY

hormogonium formation

traitmech:000651 · CLASS · PROPOSED

A morphological phenotype in which a filamentous cyanobacterium differentiates short, initially heterocyst-free filaments called hormogonia that are distinct from mature vegetative trichomes.

Trait evidence (3)

  • DOI:10.1099/00221287-111-1-1
    In all three genera, the hormogonia are initially devoid of heterocysts.

    Rippka et al. (1979), Genera of Section IV, printed pages 34-36; publisher PDF extracted text directly read, not a search-result snippet. The three genera are Nostoc, Scytonema and Calothrix. The study distinguishes differentiated hormogonia from random trichome breakage and reports immotile hormogonia in PCC 6314, 7524 and 6719. Smaller cells or gas vacuoles help identify these immotile forms; neither feature is required in every strain. Developing hormogonia can subsequently acquire terminal heterocysts, so initial absence is not permanent absence. This is a culture-based systematic study, not a universal modern taxonomic rule. PDF screenshots were unavailable; no visual panel verification or numerical table claim is made.

  • DOI:10.1128/aem.55.1.125-131.1989
    motile (gliding) filaments lacking heterocysts and with distinctly smaller cells than those of vegetative filaments

    PMID:16347816, PMC184065. Scientific Abstract directly read on PubMed and through the Europe PMC core API. Campbell and Meeks (1989) observed induced hormogonia in symbiotically competent Nostoc cultures. The quoted morphology describes those cultures, not every hormogonium. Strain 7801 underwent conversion in Anthoceros punctatus-conditioned medium under the tested conditions and later reverted to vegetative growth. The reported loss and recovery of acetylene reduction are stage-dependent readouts, not a definition requiring nitrogen fixation or plant symbiosis. Full text and panels were not read.

  • DOI:10.1128/mSphere.00231-19
    both sigC and sigJ may be required for an early stage in hormogonium development, while sigF is late acting.

    PMID:31043519, PMC6495340. Direct Europe PMC full-text XML: scientific ABSTRACT, first RESULTS subsection, and MATERIALS AND METHODS subsections Strains and culture conditions and Plasmid and strain construction were read. The snippet is from Results, not the separate precis/IMPORTANCE text. Wild-type Nostoc punctiforme formed shorter, morphologically distinct filaments after induction. In-frame sigF deletion abolished motility but retained morphological differentiation and heterocyst loss; sigC and sigJ deletions lacked those morphological markers. This separates development from locomotion experimentally. Complementation restored motility in the assay, not necessarily wild-type levels. These are strain- and assay-qualified results, not a universal sigma-factor rule inferred from sequence. Actual panels, movies and the strain-table supplement were not inspected; no panel-level or numerical claim is made.

Provenance

Identifier source
TraitMech local identifier
Definition source
DOI:10.1128/mSphere.00231-19

Parent traits (1)

kg-microbe context

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

Discussions and Knowledge Gaps (2)

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

Review the developmental scope independently of motility and mature cell shape.

CURATION TODO OPEN hormogonium-formation-scope-and-hierarchy · raised by codex · 2026-10-06

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.

Retain phenotype METPO:1000059. Motile METPO:1000702 is not a necessary parent: Rippka et al. explicitly include immotile hormogonia, and the 2019 sigF deletion retains differentiation without movement. The 1989 abstract's motile description is specific to the studied Nostoc cultures. Filament shaped METPO:1000674 denotes elongated cells or hypha-like structures, not specifically this differentiated multicellular stage. Filamentous colony METPO:1007066 denotes colony outline. Heterocyst traitmech:000073 and akinete traitmech:000185 describe other differentiated cell types, not this filament stage; their presence in a life cycle is not organism-level disjointness. Random fragmentation alone is insufficient. Do not universally require reduced cell size, gas vacuoles, permanent heterocyst absence, plant symbiosis or nitrogen fixation. Exact external equivalence and narrower hierarchy remain for human review; no xref or unqualified synonym is asserted.

Resolve strain and protein anchors before adding a causal graph or canonical example.

KNOWLEDGE GAP OPEN hormogonium-formation-stage-and-mechanism-grounding · raised by codex · 2026-10-06

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.

The cited studies support an observed developmental phenotype and genetic dependence, not merely sequence-feature possession. Before adding a mechanistic graph, inspect actual panels and supplements, resolve accession-level sigma-factor examples, and distinguish induction, morphological differentiation and motility readouts. Transcript changes or homologous sig genes alone do not establish the phenotype or the complete cascade. Canonical examples are deferred pending strain-table and taxon verification with natural provenance and explicit life-stage qualifiers; engineered deletion strains must not be presented as unqualified natural exemplars. The known mechanism is not claimed to be absent, and natural transient stages remain valid trait evidence without a canonical row.

Curation history

  1. · MINTED_TRAITMECH_ID · codex

    Added hormogonium formation with three DOI-backed snippets and explicit developmental-stage, motility and sequence-inference limits. Ignored-and-hidden novelty searches and the pinned METPO audit found no exact record. Reserved METPO:1060400 in v527. Deferred unresolved strain/protein anchors; existing records unchanged.