ejectosome
An ejectosome is a cellular organelle responsible for ejecting their contents from the cell. Two unrelated types of ejectosomes are described in the literature:
- Cryptomonads have two types of characteristic extrusomes known as ejectosomes.
- 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.{{Cite web |url=http://www.botany.ubc.ca/Biol320/ultra/whol11.htm |title=Cryptophyte With Ejectosome Electron Micrograph. |access-date=2009-06-10 |archive-url=https://web.archive.org/web/20110613114553/http://www.botany.ubc.ca/Biol320/ultra/whol11.htm |archive-date=2011-06-13 |url-status=dead }} 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{{Citation needed|date=September 2023}}. Large ejectisomes, visible under the light microscope, are associated with the pocket; smaller ones occur elsewhere on the cell.[http://tolweb.org/Cryptomonads/2396 Cryptomonads = Goniomonas + plastid-containing cryptophytes.]
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.[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.]