Ultrastructural insights into the polar tube invasion organelle from microsporidian parasites

Paris R Watson; Damian C Ekiert; Gira Bhabha

doi:10.1016/j.mib.2026.102762

Ultrastructural insights into the polar tube invasion organelle from microsporidian parasites

Curr Opin Microbiol. 2026 May 4:91:102762. doi: 10.1016/j.mib.2026.102762. Online ahead of print.

Authors

Paris R Watson¹, Damian C Ekiert², Gira Bhabha³

Affiliations

¹ Department of Biology, Johns Hopkins University, Baltimore, MD, USA.
² Department of Biology, Johns Hopkins University, Baltimore, MD, USA. Electronic address: damian.ekiert@be-labs.org.
³ Department of Biology, Johns Hopkins University, Baltimore, MD, USA. Electronic address: gira.bhabha@be-labs.org.

PMID: 42085890
DOI: 10.1016/j.mib.2026.102762

Abstract

Microsporidia are single-celled intracellular parasites that infect a wide range of animals, including humans. To invade host cells, microsporidia have evolved a harpoon-like invasion apparatus called the polar tube (PT). Initially neatly coiled inside dormant spores, when triggered, the PT rapidly fires out of the spore, transforming into a linear tube that impales or mediates attachment to a nearby host cell. The linear PT then serves as a conduit for the delivery of the infectious parasite cell to the interior of the host cell. While the PT was discovered more than 120 years ago, the composition, structure, and mechanism of this fascinating invasion organelle remain poorly understood. Recent developments in cryoelectron tomography have enabled new investigations of the PT, yielding fresh insights into its organization and ultrastructure. Here, we review our current understanding of the PT invasion organelle, with a focus on its ultrastructure in the pre-firing state (when coiled in the dormant spore) and post-firing state (after exit from the spore).

Publication types

Review