microsporidian posterior vacuole

cellstructuremech:microsporidian_posterior_vacuole · Membrane organelle · Membrane bounded organelle · Proposed

A membrane-bounded posterior vesicle in a microsporidian spore that expands during germination and is implicated in polar-tube extrusion and sporoplasm expulsion. [DOI:10.14411/fp.2005.014]

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
posterior vacuole membrane	Lipid	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Membrane boundary that encloses the posterior vacuole in mature microsporidian spores. `DOI:10.14411/fp.2005.014` Findley et al. 2005 directly studied the Spraguea lophii posterior vacuole during spore hatching. `DOI:10.1371/journal.ppat.1008738` Jaroenlak et al. 2020 visualized the Anncaliia algerae posterior vacuole by serial block-face scanning electron microscopy and electron tomography.

Taxonomic distribution

NCBITaxon:6029 Microsporidia — COMMON: The posterior vacuole is modeled as a microsporidian infectious-spore organelle, not as a structure present in every intracellular vegetative stage. [DOI:10.1007/978-3-030-93306-7_9]

Canonical examples

NCBITaxon:6039 Vairimorpha necatrix — Moth-infecting microsporidian whose germinating spores were imaged by cryo-electron tomography during polar-tube extension and sporoplasm expulsion. [DOI:10.1371/journal.pbio.3002533]

Functions

polar tube firing support — During spore germination, posterior vacuole expansion is coupled to pressure changes and movement of spore contents toward the everting polar tube.
- DOI:10.14411/fp.2005.014 Findley et al. 2005 tested the posterior vacuole's role in Spraguea lophii spore hatching.
- DOI:10.1016/j.fgb.2015.08.007 Troemel and Becnel 2015 observed posterior vacuole expansion late in Edhazardia aedis polar-tube firing.

Mechanism graphs

Posterior vacuole expansion accompanies polar-tube firing (FUNCTION)

The posterior vacuole sits behind the sporoplasm in mature microsporidian spores. During germination it expands as the polar tube fires, a nonmechanistic relationship consistent with a role in moving spore contents into the everting polar tube.

Subject	Predicate	Object	Evidence
posterior vacuole membrane	encloses	microsporidian posterior vacuole	`DOI:10.14411/fp.2005.014` Findley et al. 2005 studied the membrane-bounded posterior vacuole of Spraguea lophii spores. `DOI:10.1371/journal.ppat.1008738` Jaroenlak et al. 2020 resolved the posterior vacuole as a distinct organelle in three-dimensional reconstructions.
microsporidian posterior vacuole	resides at	posterior spore pole	`DOI:10.1371/journal.ppat.1008738` Jaroenlak et al. 2020 reconstructed the posterior vacuole in Anncaliia algerae spores.
microsporidian posterior vacuole	expands during	polar tube firing	`DOI:10.1016/j.fgb.2015.08.007` Troemel and Becnel 2015 observed an expanding posterior vacuole in the final frames of Edhazardia aedis polar-tube firing. `DOI:10.14411/fp.2005.014` Findley et al. 2005 connected the Spraguea lophii posterior vacuole to spore hatching.
microsporidian posterior vacuole	pushes	sporoplasm	`DOI:10.1016/j.fgb.2015.08.007` Troemel and Becnel 2015 interpreted late posterior-vacuole expansion as pushing spore contents into the everted polar tube. `DOI:10.1371/journal.pbio.3002533` Sharma et al. 2024 imaged the sequence of microsporidian polar-tube firing and sporoplasm expulsion in Vairimorpha necatrix.

Discussions

CURATION_TODO (OPEN): Resolve exact posterior vacuole membrane and lumenal composition. The current record captures the membrane-bounded organelle and its expansion phenotype, but it does not identify exact lipid species, lumenal osmolytes, or proteins that drive posterior vacuole swelling.

Evidence

DOI:10.14411/fp.2005.014 Findley et al. 2005, Role of the posterior vacuole in Spraguea lophii (Microsporidia) spore hatching, Folia Parasitologica.
DOI:10.1016/j.fgb.2015.08.007 Troemel and Becnel 2015, Genome analysis and polar tube firing dynamics of mosquito-infecting microsporidia, Fungal Genetics and Biology.
DOI:10.1371/journal.ppat.1008738 Jaroenlak et al. 2020, 3-Dimensional organization and dynamics of the microsporidian polar tube invasion machinery, PLOS Pathogens.
DOI:10.1007/978-3-030-93306-7_9 Jaroenlak, Usmani, Ekiert and Bhabha 2022, Mechanics of Microsporidian Polar Tube Firing, Experientia Supplementum.
DOI:10.1371/journal.pbio.3002533 Sharma et al. 2024, Ultrastructural insights into the microsporidian infection apparatus reveal the kinetics and morphological transitions of polar tube and cargo during host cell invasion, PLOS Biology.

Curation history

2026-09-13T11:42:29Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-13T11:43:08Z codex · EXPANDED_RECORD — Added the label-only posterior vacuole membrane component, Microsporidia and Vairimorpha necatrix scope, a polar-tube firing support function, posterior-vacuole DOI evidence, a nonmechanistic expansion graph, and a composition-grounding TODO.
2026-09-13T11:49:31Z codex · ADDRESSED_PR_REVIEW — Resolved PR #777 review issue #778 by adding a posterior-vacuole membrane node, moving component_ref off the organelle node, adding a polar-tube-firing process node, and retargeting the expansion edge to that process.

Source: data/structures/membrane_organelle/microsporidian_posterior_vacuole.yaml