First published online August 23, 2004
Journal of Experimental Biology 207, 3349-3359 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01167
Bioconvective pattern formation of Tetrahymena under altered gravity
Yoshihiro Mogami1,*,
Akiko Yamane2,
Atsuko Gino1 and
Shoji A. Baba2
1 Department of Biology, Ochanomizu University, Otsuka 2-1-1, Tokyo
112-8610, Japan
2 Graduate School of Humanities and Sciences, Ochanomizu University, Otsuka
2-1-1, Tokyo 112-8610, Japan
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Fig. 1. Gravity-dependent pattern formation of Tetrahymena pyriformis
enclosed in a circular glass chamber 2 mm deep at a density of
1.0x106 cells ml-1. (A) Plan view of the
suspension under subcritical (a), threshold (b) and supracritical (c)
conditions for pattern formation with increase in gravity. Regions with higher
cell densities appear as bright white areas under dark field illumination. A
linear region indicated by faced arrows is the portion on which space-time
plots in (B) and (C) were made. Bar, 10 mm. (B) Space-time plot of an
experiment of increasing gravity and the corresponding gravity profile.
Letters a-c indicate the time corresponding to respective plan views a-c shown
in A. (C) Space-time plot of an experiment of decreasing gravity and the
corresponding gravity profile. Horizontal and vertical bars in B and C are 1
min and 10 mm, respectively. Broken lines in B and C indicate threshold levels
for increasing and decreasing gravity, respectively.
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Fig. 2. (A) Plan view of a steady state bioconvective pattern prepared for Fourier
analysis as described in Materials and methods. A typical pattern developed
under control gravity (1.01 g) in a suspension of T.
pyriformis (1x106 cells ml-1 in a 4 mm deep
glass chamber). Regions of higher cell densities appear as bright white areas
under dark field illumination. Bar, 10 mm. (B) 2D FFT of A after applying a
Hann window filter. (C) Radial spectrum density of the pattern in B (solid
line) as a function of wave number (per 72.5 mm) and the result of
least-squares fitting of an unnormalized biased Gaussian function (broken
line) (r2=0.92, P<0.001). (D) 2D FFT of the
image recorded under hypergravity (2.09 g), which is shown in
Fig. 3A. (E) Radial spectrum
density of the pattern in D (solid line) and the result of least-squares
(broken line) (r2=0.97, P<0.001).
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Fig. 3. Plan views of steady state bioconvective patterns developed under various
gravities and recorded with suspensions of T. pyriformis (A), T.
thermophila (B) and TNR (C). These suspensions were placed in a 4 mm deep
glass chamber at a density of 1x106 cells ml-1.
Numbers indicate the magnitude of applied gravity in g. The
mean wave numbers obtained by Fourier analysis from these pictures are shown
by filled symbols in Fig. 4.
Bar, 10 mm.
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Fig. 4. Profiles of changes in the mean wave number with stepwise changes in
gravity obtained from the suspension of T. pyriformis (A), T.
thermophila (B) and TNR (C). The mean wave number (circles) and the
corresponding profile of altered gravity (solid lines) are shown as a function
of time. The mean wave number (left ordinate) has been scaled in relation to
the magnitude of changes in gravity (right ordinate). Filled symbols
correspond to the wave numbers of the patterns shown in
Fig. 3. Bars, 1 min.
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Fig. 5. Mean wave number of bioconvective patterns as a function of the magnitude
of applied gravity step. The average of the mean wave numbers measured within
each gravity step from T. pyriformis (triangles), T.
thermophila (filled squares) and TNR (circles) are shown ±
S.D.
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© The Company of Biologists Ltd 2004
