Date of Award


Document Type


Degree Name

Master of Science (MS)


Biomedical Sciences


This research was undertaken to determine the effect on growth of Tetrahymena pyriformis of a single stress followed at some later time by a second stress, using temperature change and osmotic pressure change as stress factors.

Growth rate of T. pyriformis was determined under standard conditions of temperature and osmotic pressure (29°C and 100 milliosmols). A single stress consisting of a decrease in temperature to 20°C or an increase in osmotic pressure to 300 milliosmols was applied to an exponentially growing culture and its effect noted. After a recovery period a second, different stress was applied to the culture J and its effect noted.

Prom results of these experiments the following conclusions were reached: (1) Either single stress caused a k, brief lag, followed by resumption of exponential growth at a lesser rate. (2) The order in which the stresses were applied did not change their overall effect on growth. (3) The most obvious effect of the double stress was a lengthening of the lag period. (4) The organisms adapted more quickly to the two stresses when a recovery period was allowed between stresses than when both were applied simultaneously.