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Journal of Experimental Biology 60,605-629 (1974)
Published by Company of Biologists 1974

Effects of Pressure and Temperature Changes on the Flagellar Movement of Crithidia Oncopelti

C. J. COAKLEY ¹ and M. E. J. HOLWILL ¹

¹ Physics Department, Queen Elizabeth College, University of London, London, W. 8

1. The combined effects of hydrostatic pressure and temperature on the flagellar movements of Crithidia oncopelti were studied.

2. Provided that a critical pressure, which depended on the temperature, was not exceeded, the application of pressure produced an initial increase in flagellar frequency ; the frequency then fell to a steady level which was below the value obtaining before the application of pressure.

3. The compression also caused a transient increase in the number of organisms propagating coherent waves, an increase in the average wave amplitude, and asymmetric waveforms with decreasing wavelength and amplitude towards the flagellum tip.

4. The results are consistent with the hypotheses that the observed flagellar response is due to (a) changes in the equilibrium of a reversible enzyme denaturation process, and (b) changes in the rate of decomposition of an enzyme-substrate complex.

5. Values of the volume, enthalpy and entropy changes associated with each process are derived and their significance for mechanism is discussed.

Note:

Throughout this paper the S.I. unit of pressure, the pascal (Pa), will be used, 1 Pa=1 N m^-2; 1 atmosphere=101 325 N m^-2 10⁵ Pa=0.1 MPa.