Date of Award

Spring 2005

Document Type

Restricted Thesis

Terms of Use

© 2005 Aparna Kishor. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts


Biology Department


The safe and inexpensive control of microbes in food and water supplies is critical for maintaining a healthy population. Besides using chemicals and radiation to effect such control, ultrasound may be a valuable tool. In this study, two different treatment strategies were explored for bacteria in liquid culture: the first was to use ultrasound alone (1 MHz, 8.51 MPaₚₚ with a total exposure time of 45 minutes per sample) and the second was to combine insonification and simultaneous treatment with hydrogen peroxide (10 minute exposure to 1.08 MHz, 17 MPaₚₚ at a 2.5% duty cycle with hydrogen peroxide concentrations particular to each species). Viability was determined by dilution plating. Twenty bacterial species representing a variety of morphologies and metabolisms were subjected to these two treatment regimes. Insonification alone resulted in the reduction of bacterial cultures by up to two orders of magnitude for many strains, and as high as six for some. Results, however, were inconsistent. When ultrasound was used in combination with treatment by hydrogen peroxide, there was a synergistic effect on growth reduction for some strains.