First published online August 30, 2006
Journal of Experimental Biology 209, 3580-3586 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02426
Correlation between thermotolerance and membrane properties in Paramecium aurelia
Toshiaki Sasaki1,
Yoshimi Konoha2,
Taichi Toyoda2,
Yuta Yasaka3,
Eva Przybos4 and
Yasuo Nakaoka1,*
1 Biophysical Dynamics Laboratories, Graduate School of Frontier Bioscience,
Osaka University, Toyonaka, Osaka 560-8531, Japan
2 Division of Biophysical Engineering, Graduate School of Engineering
Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
3 Research Center for Environmental Preservation, Osaka University, Suita,
Osaka 565-0871, Japan
4 Department of Experimental Zoology, Institute of Systematics and Evolution
of Animals, Polish Academy of Sciences, Slawkowska 17, 31-016 Krakow,
Poland
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Fig. 1. Comparison of thermotolerance between P. aurelia syngens. Each
syngen, cultured at 25°C, was incubated at 33°C for 30 min, and then
the incubation temperature was raised stepwise by 1°C and kept constant
for about 10 min. At each temperature, swimming cells were counted and the
temperature at which no cells were swimming was determined as the killing
temperature. Experiments were conducted three times.
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Fig. 2. Comparison of membrane resistance between P. aurelia syngens.
Cells cultured at either 25°C or 35°C were deciliated 30 min before
the measurement and suspended in a standard solution at each culture
temperature. The resting potentials of syngens were in the range, -24 mV to
-29 mV. Membrane resistance was measured at 25°C by application of a
constant inward current (10-10 A). Key indicates culture
temperature. Each value for membrane resistance is the mean ± s.d.
(N=5-10 cells).
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Fig. 3. Typical examples of laurdan-labeled P. aurelia and GP
image. (A) Fluorescence image of laurdan-labeled P. aurelia. Syngen
10 cells were labeled with laurdan and observed at 25°C. The photograph
was taken with a 4 s exposure using a digital camera. Scale bar, 50 µm. (B)
GP map image calculated from fluorescence images of syngen 2 cell at
25°C. The GP value of each pixel was measured within the circle
(diameter, 20 µm). (C) Colour bar and histogram of GP values
obtained from (B). Total counts: 8730, bin width: 0.006. GP value was
determined from the mean of the histogram.
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Fig. 4. Temperature dependence of GP value. P. aurelia syngens,
2, 3, 8 and 10 cells were cultured at 25°C. Fluorescence image of
laurdan-labeled cells was initially taken at 25°C, and then taken 3 min
after the temperature shift to either 35°C or the killing temperature of
each syngen. Images were taken before the cell death. GP values are
the means ± s.d. (N=5-8 cells).
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Fig. 5. Fatty acid composition of various syngens. P. aurelia syngens, 2,
3, 8 and 10 were cultured at either 20°C or 30°C. Fatty acids
extracted from whole cells were analyzed by HPLC as described in Materials and
methods. The fatty acids are denoted by the convention C with the ratio of the
number of carbon atoms to the number of unsaturated linkages. (A) Syngen 2.
(B) Syngen 3. (C) Syngen 8. (D) Syngen 10. Key indicates culture temperature.
Values are the mean ± s.d. (N=3-6 experiments).
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Fig. 6. Ratio of unsaturated to saturated fatty acids. Fatty acid compositions
shown in Fig. 5 were divided
into unsaturated and saturated fatty acids, and expressed as a ratio. Key
indicates culture temperature. Values are the means ± s.d.
(N=3-6 experiments).
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© The Company of Biologists Ltd 2006
