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Structural Evidence for Actin-like Filaments in Toxoplasma gondii Using High-Resolution Low-Voltage Field Emission Scanning Electron Microscopy

Published online by Cambridge University Press:  01 August 2003

Heide Schatten
Affiliation:
Department of Veterinary Pathobiology, University of Missouri-Columbia, 1600 East Rollins Street, Columbia, MO 65211, USA
L. David Sibley
Affiliation:
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
Hans Ris
Affiliation:
Department of Zoology, University of Wisconsin, Madison, WI 53706, USA
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Abstract

The protozoan parasite Toxoplasma gondii is representative of a large group of parasites within the phylum Apicomplexa, which share a highly unusual motility system that is crucial for locomotion and active host cell invasion. Despite the importance of motility in the pathology of these unicellular organisms, the motor mechanisms for locomotion remain uncertain, largely because only limited data exist about composition and organization of the cytoskeleton. By using cytoskeleton stabilizing protocols on membrane-extracted parasites and novel imaging with high-resolution low-voltage field emission scanning electron microscopy (LVFESEM), we were able to visualize for the first time a network of actin-sized filaments just below the cell membrane. A complex cytoskeletal network remained after removing the actin-sized fibers with cytochalasin D, revealing longitudinally arranged, subpellicular microtubules and intermediate-sized fibers of 10 nm, which, in stereo images, are seen both above and below the microtubules. These approaches open new possibilities to characterize more fully the largely unexplored and unconventional cytoskeletal motility complex in apicomplexan parasites.

Type
Biological Applications
Copyright
© 2003 Microscopy Society of America

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