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The tachyzoites (pictured here in a characteristic rosette pattern) are the motile stage of the Toxoplasma gondii life cycle. They are powered by the “glideosome”—an actomyosin engine situated just beneath the plasma membrane that enables the tachyzoite to move through biological tissues, to penetrate cells of the host in order to initiate infection, and to subsequently escape from within the cells they have infected. Understanding the mechanisms of such “molecular motors” will aid in interrupting the life cycles of these human pathogens, and controlling such diseases as toxoplasmosis and malaria, which is caused by Plasmodium falciparum, another parasitic protozoan in the phylum Apicomplexa.
For more on toxoplasmosis watch “The Cat Parasite That Tricks Rat Brains: Microbe Minute”
The tachyzoites were cultured in fibroblasts, and subsequently stained for a glideosome-associated protein (in red) and a protein associated with the inner membrane complex (in green), and imaged with a laser scanning confocal microscope. Each tachyzoite is 7 mm in length—around the size of a red blood cell.
Karine Frenal, PhD and HHMI International Research Scholar Dominique Soldati-Favre PhD, Department of Microbiology and Molecular Medicine, CMU, University of Geneva, Switzerland