Dynamics of polar filament discharge and sporoplasm expulsion by microsporidian spores
Article first published online: 4 FEB 2005
Copyright © 1992 Wiley-Liss, Inc.
Cell Motility and the Cytoskeleton
Volume 22, Issue 1, pages 38–50, 1992
How to Cite
Frixione, E., Ruiz, L., Santillán, M., de Vargas, L. V., Tejero, J. M. and Undeen, A. H. (1992), Dynamics of polar filament discharge and sporoplasm expulsion by microsporidian spores. Cell Motil. Cytoskeleton, 22: 38–50. doi: 10.1002/cm.970220105
- Issue published online: 4 FEB 2005
- Article first published online: 4 FEB 2005
- Manuscript Accepted: 6 DEC 1991
- Manuscript Received: 16 SEP 1991
- invasion mechanisms;
- kinematic analysis;
- protoplasm flow;
- video microscopy
Spores of the microsporidium Nosema algerae were stimulated to germinate in vitro while observed with video-enhanced contrast microscopy. Field-by-field playback of tape-recorded sequences yielded the first serial illustrations and kinematic analysis of the explosive discharge of the polar filament and the sporoplasm. The filament emerges from the anterior pole of the spore in a regularly pitched helicoidal course along a nearly straight axis, with a mean maximum instant velocity of 105 μm/s. Just before elongation is completed the filament tip follows a tortuous path that often results in a curved or spiralling terminal configuration. Then elongation stops and, after a lag that may vary from less than 15 to over 500 ms, the sporoplasm pours out at the filament tip forming a globule that quickly grows up to a size larger than its original volume within the spore. Concomitantly, the helical filament becomes straightened and frequently the spore body is pulled forward. Thereafter a relaxed filament, usually 5–10% shorter than when maximally extended, remains connecting the empty spore case and the sporoplasmic droplet. Experiments with hyperosmolar media produced a considerable slowdown of filament extrusion and often precluded sporoplasm discharge. The present results are fully consistent with the hypothesis of a hydrostatic pressure-triggered mechanism of spore germination, and revealed that the process is composed of two discrete phases separated by a variable lag: (1) complete eversion of the polar filament, and (2) passage of the main sporoplasm mass along the tube. The data provide a preliminary basis toward the conception of a quantitative physical model of microsporidian spore germination. © 1992 Wiley-Liss, Inc.