Ultrasonic Radiation and Yeast Cells

Abstract

A system capable of producing a series of high frequency waves in fluid may be constructed by placing a piezoelectric crystal of carefully prepared quartz in a di-electric liquid such as xylol. A pair of electrodes is then placed upon opposite sides of the quartz crystal and should be connected with a high frequency oscillator. Such an arrangement of apparatus allows one to set up compression waves even of radio frequency in the liquid. A system similar to this has been described by Wood and Loomis. 1 Radiation by the resultant ultrasonic vibration has been shown by Wood and Loomis 1 to be destructive to certain varieties of organisms including algae, but it was their opinion that bacteria are not injured by such treatment. Radiation by ultrasonic vibration may be attended by cavitation of included gases and it is considered probable by Johnson 2 and by Schmitt and Uhlemeyer 3 that this mechanical expulsion of the gases is the cause of disruption of living cells. Recent observations of Wu and Liu 4 indicate that these rays coagulate protein and thus it becomes probable that protein changes contribute to the cause of death.

To test the effects of ultrasonic radiation upon yeasts, the following series of experiments was performed: A wine yeast was incubated in grape juice for 24 to 48 hours at 37°C. This organism, listed in our cultures as a Saccharomyces elliposoideus, was chosen because of its relatively large size and active growth.

Treatment was carried out by placing the culture to a depth of approximately one inch within a glass tube 1 1/2 inches in diameter. The bottom of this tube, however, was of heavy cellophane cemented to the side walls.