kappa particles

kap·pa par·ti·cles

inheritable cytoplasmic symbionts, once thought to be particles mainly or exclusively of DNA, occurring in some strains of Paramecium; capable of producing a product lethal to other strains.
Farlex Partner Medical Dictionary © Farlex 2012

kappa particles

the bacteria that inhabit the cytoplasm of the ciliate Paramecium aurelia. Kappa-free Paramecia are sensitive to toxins produced by the particles, dying when exposed to them, after CONJUGATION. Kappa carriers (called killer stocks) are immune to the toxin.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
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