Multiple-exposure photographic analysis of a motile spirochete.

Abstract

The Leptospiraceae are thin spirochetes with a unique mode of motility. These spiral-shaped bacteria have internal periplasmic flagella that propel the cells in lowviscosity and gel-like high-viscosity media. A model of Leptospiraceae motility has been previously proposed that states that the subterminally attached periplasmic flagella rotate between the outer sheath and the helical protoplasmic cylinder. The shape of the cell ends and the direction of gyration of these ends are determined by the direction of rotation of the internal periplasmic flagella. Rotation of the periplasmic flagella in one direction causes that end to be spiral-shaped, and rotation in the other direction causes that end to be hook-shaped. One prediction of the model is that these right-handed spirochetes roll clockwise when swimming away from an observer. For maximum swimming efficiency, the model predicts that the sense of the spiral-shaped end is left-handed and gyrates counterclockwise. The present study presents direct evidence that the cell rolls clockwise (protoplasmic cylinder helix diameter = 0.24 ,jm; pitch = 0.69 jam), the ends gyrate counterclockwise, and the spiral-shaped end is left-handed (helix diameter = 0.6 jam; pitch = 2.7 ,jm)-as predicted by the model. The hook-shaped end appears approximately planar. The approach used was to illuminate stroboscopically cells slowed by Ficoll and analyze the resultant multiple-exposure photographs focused above and below the axis of the cell. The methodology used should be helpful in analyzing the motility of the larger and more complex spirochetes.

The bent-end morphology of Treponema phagedenis is associated with short, left-handed, periplasmic flagella

“…Members of the family Leptospiraceae swim by a mechanism that is somewhat different from that proposed for S. aurantia but that still assumes that the PFs rotate between the outer membrane sheath and the cell cylinder (3,11,13,21,22). In the Leptospiraceae, the single PF attached subterminally at each end of the cell cylinder is coiled and does not overlap in the center of the cell with the other PF (5,10,26).…”

“…The PFs from these mutants no longer coiled, and the ends of these mutant cells were straight (10). These results led to a model of Leptospiraceae motility (3), and recent evidence supports this model (13,21,22).…”

“…In the Leptospiraceae, the single PF attached subterminally at each end of the cell cylinder is coiled and does not overlap in the center of the cell with the other PF (5,10,26). Translating cells have spiral-shaped anterior ends and hook-shaped posterior ends (3,13,21,22); the ends of nontranslating cells are either both hook shaped or both spiral shaped (3,13,21). Motility mutants which concomitantly had an altered cell morphology and PF shape were isolated.…”

“…Photographs were taken and analyzed by techniques similar to those described previously (22). For photographs of live T. phagedenis, a cover glass supported on two sides with a mixture of Vaseline and paraffin was placed on a slide and a drop of cells in growth medium was allowed to flow under the cover glass.…”

“…1). The radius of curvature was calculated from dark-field micrographs as previously described (22). Lengths of sine waves of a given amplitude and wavelength were computed by numerical integration.…”