FLAGELLAR SURFACE MOTILITY - GLIDING AND MICROSPHERE MOVEMENTS

Flagella are generally thought to promote whole-cell locomotion through the initiation and propagation of bends along the organelle. Chlamydomonas and certain other flagellated protists provide a striking exception to this rule. While Chlamydomonas species can clearly swim through liquid medium by the coordinated initiation and propagation of bends along their two flagella, this is probably not the physiologically most relevant form of whole-cell locomotion for these cells. Chlamydomonas exhibit whole-cell locomotion along a solid substrate, be it soil, glass or agar. This is referred to as gliding motility. Gliding motility is exhibited by all flagellated stages of Chlamydomonas. During the course of gliding motility, the flagella can appear to be absolutely straight and immotile, exhibiting no obvious bends or undulations. On occasion, however, the distal 1 μm of the leading flagellum can be seen to wiggle; this observation, coupled with the fact that cells can glide in curved trajectories, suggests the possibility that Chlamydomonas can regulate the direction of gliding motility. A wide variety of paralyzed flagellar strains, exhibit normal gliding behavior, suggesting that gliding motility is not coupled to axonemal motility and is not dependent on the motor responsible for axonemal motility and flagellar beating, also involvement of a minus end-directed micro-tubule-associated motor. This chapter discusses procedures for observing gliding motility and polystyrene microsphere movements. Nongliding cell strains of Chlamydomonas were unable to exhibit microsphere movement along the flagellar surface, suggesting that microsphere movements are a manifestation of the same force transduction system responsible for whole-cell gliding motility. Attachment to and movement along the flagellar surface of polystyrene microspheres provides an easy, quantitative assay for the force transduction system responsible for gliding motility. Availability of nongliding mutants, especially that have been insertionally tagged, provides the opportunity to identify genes whose products are involved in this form of whole-cell locomotion. © 1995, Academic Press Inc.