Ejectosome

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title: "Ejectosome" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["organelles"] topic_path: "general/organelles" source: "https://en.wikipedia.org/wiki/Ejectosome" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

An ejectosome is a cellular organelle responsible for ejecting their contents from the cell. Two unrelated types of ejectosomes are described in the literature:

  1. Cryptomonads have two types of characteristic extrusomes known as ejectosomes.
  2. Intracellular pathogens, such as Mycobacterium tuberculosis, escape from their host cells using an actin-based structure, also called an ejectosome.

Cryptomonad ejectosomes contain two connected spiral ribbon-like structures, held under tension. If the cells are irritated either by mechanical, chemical or light stress, they discharge, propelling the cell in a zig-zag course away from the disturbance. Large ejectisomes, visible under the light microscope, are associated with the pocket; smaller ones occur elsewhere on the cell.

Mycobacteria are ejected from host cells through the action of an actin-based ejectosome. This escape mechanism requires a cytoskeleton regulator from the host plus an intact mycobacterial ESX-1 secretion system. Ejectosomes apparently exert a contractile force, forming a tight septum around the bacteria. Ejection of the bacteria occurs without host cell lysis.

References

References

  1. "Cryptophyte With Ejectosome Electron Micrograph.".
  2. [http://tolweb.org/Cryptomonads/2396 Cryptomonads = Goniomonas + plastid-containing cryptophytes.]
  3. [http://www.sciencemag.org/cgi/content/abstract/323/5922/1729?ck=nck Hagedorn, M. et al. Infection by Tubercular Mycobacteria Is Spread by Nonlytic Ejection from Their Amoeba Hosts. Science 27 March 2009: Vol. 323. no. 5922, pp. 1729 - 1733.]

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organelles