Date of Award

Spring 1997

Document Type

Restricted Thesis

Terms of Use

© 1997 Elizabeth Glater. 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




Oxidative stress is an accumulation of reactive oxygen species which can be toxic to the cell. In Escherichia coli, the expression of katG, encoding catalase, hydroperoxidase I, is induced in response to oxidative stress. In this experiment, the expression of katG was studied using a lux reporter system in cells during different growth conditions, log and stationary phase, and cells that were grown anaerobically and then exposed to oxygen. As expected, stationary phase cells were more resistant to oxidative stress than log phase cells and exhibited lower katG expression. The spent media from stationary phase cultures was shown to confer resistance to log phase cells. Cells grown aerobically and then exposed to oxygen and hydrogen peroxide had much higher levels of katG expression than those grown aerobically. The expression of katG was also measured in rpoS- and oxyR- mutant strains during different growth conditions because these genes have been shown to regulate katG. As shown in previous studies, katG expression was much lower in the oxyR- in both log and stationary phase compared to wild type cells. As in previous studies, katG expression was similar in the rpoS- strain and wild type during log phase, but in contrast to previous studies, katG expression was higher in the rpoS- mutant than wild type during stationary phase. In addition, cells treated with antioxidants, vitamin C and salicylic acid, were shown to reduce katG expression.