4 Notes
1. Since swimming abilities of spirochetes including Leptospira are
known to be enhanced with an increase in viscosity, investigating viscosity dependencies of their motility parameters would
lead to deeper understanding of the motility mechanism. When
using polymers, note types of polymer. A major point when
selecting a polymer in motility assays of Leptospira is whether
the polymer solution is viscoelastic. According to verification
by Berg and Turner [17], the addition of Ficoll, a branched
polymer, to liquid makes homogeneous viscous solution,
whereas methylcellulose forms a heterogeneous network in
liquid, which is a gel-like, viscoelastic solution. Previous studies
have shown that the swimming velocity of Leptospira is
decreased monotonically with the increased Ficoll concentration but is increased with the concentration of methylcellulose
[4, 18]. Numerical simulations based on a hydrodynamic theory predict that the observed differences between Ficoll and
methylcellulose are attributed to differences in microscopic
structure of viscous liquids, i.e., highly branched or gel-like
structure [19, 20]. Viscosities of epithelium mucus layer in
the cecum and colon of porcine are 7–12 mPa  s [21]. Since
Fig. 5 Observation of the protoplasmic cylinder rotation by bead assay. (a) The upper schematic depicts a cell
(black wavy line) labeled with an antibody-coated bead (red circle). The lower-left panel shows the bead
trajectory (red arrow) by a superposition of sequential video images. The lower-right panel shows the time
course of the bead position from the data shown in the left. In this data, the periodic change in the Y position
indicates the bead rotation. (b) The montage displays the bead rotation, and the sequential diagram draws the
rotational direction. (c) The focal plane of observation is essential information to determine the rotational
direction of beads, which can be deduced from the visualized helix angle of PC (yellow arrows). (d) The bead
movements in the Z-axis direction under dark-field microscope change the area of the bead images (halation).
The X-axis indicates image numbers shown in b, which is useful to determine the rotational direction, too. The
original data are shown in ref. 2
146
Shuichi Nakamura
1. Since swimming abilities of spirochetes including Leptospira are
known to be enhanced with an increase in viscosity, investigating viscosity dependencies of their motility parameters would
lead to deeper understanding of the motility mechanism. When
using polymers, note types of polymer. A major point when
selecting a polymer in motility assays of Leptospira is whether
the polymer solution is viscoelastic. According to verification
by Berg and Turner [17], the addition of Ficoll, a branched
polymer, to liquid makes homogeneous viscous solution,
whereas methylcellulose forms a heterogeneous network in
liquid, which is a gel-like, viscoelastic solution. Previous studies
have shown that the swimming velocity of Leptospira is
decreased monotonically with the increased Ficoll concentration but is increased with the concentration of methylcellulose
[4, 18]. Numerical simulations based on a hydrodynamic theory predict that the observed differences between Ficoll and
methylcellulose are attributed to differences in microscopic
structure of viscous liquids, i.e., highly branched or gel-like
structure [19, 20]. Viscosities of epithelium mucus layer in
the cecum and colon of porcine are 7–12 mPa  s [21]. Since
Fig. 5 Observation of the protoplasmic cylinder rotation by bead assay. (a) The upper schematic depicts a cell
(black wavy line) labeled with an antibody-coated bead (red circle). The lower-left panel shows the bead
trajectory (red arrow) by a superposition of sequential video images. The lower-right panel shows the time
course of the bead position from the data shown in the left. In this data, the periodic change in the Y position
indicates the bead rotation. (b) The montage displays the bead rotation, and the sequential diagram draws the
rotational direction. (c) The focal plane of observation is essential information to determine the rotational
direction of beads, which can be deduced from the visualized helix angle of PC (yellow arrows). (d) The bead
movements in the Z-axis direction under dark-field microscope change the area of the bead images (halation).
The X-axis indicates image numbers shown in b, which is useful to determine the rotational direction, too. The
original data are shown in ref. 2
146
Shuichi Nakamura