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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 3781

Klaus Heckmann; [Omikron, ein essentieller Endosymbiont von Euplotes aediculatus]. J.Protozool. 22(1):97-104, 1975

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The fresh water ciliate Euplotes aediculatus contains in its cytoplasm 900-1000 rod-shaped symbiotes which appear to be essential for divison. Growth of Euplotes in the presence of penicillin results in loss of these symbiotes and simultaneously in a loss of the ciliate's ability to divide. Reinfection with the symbiotes can be achieved in 4% of the cells which then resume growth after a lag period of 4-5 days. The endosymbiotes have been studied by light and electron microscopy. In their fine structure and staining reaction they resemble gram-negative bacteria as do kappa and other killer particles of Paramecium. The symbiotes of Euplotes, however, are unusual in that their DNA is not distributed throughout the cytoplasm but is localized in 3-9 areas (nucleoids), which are visible even in the light microscope. No killing activity seems to be associated with the symbiotes. Following the practice of referring to those endosymbiotes by Greek letters they are here designated omikron particles.