Date of Award

Spring 2006

Document Type

Restricted Thesis

Terms of Use

© 2006 Alexander F. Glick. 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

Department

Biology Department

First Advisor

Amy Cheng Vollmer

Abstract

The universal stress protein A (uspA), gene in Escherichia coli is expressed in response to many different stresses, although its exact function is unknown. Studying uspE, one of several uspA paralogs, may shed more light on the role of the uspA family of genes. This study characterized the viability and stress response of strains lacking the uspA and uspE genes. Wild type and null mutant strains were tested for survival under a variety of lethal stress conditions (extended stationary phase, heat shock, genotoxic damage, oxidative damage, osmotic shock, and DNA gyrase inhibition) at exponential and stationary phases of growth; viability of stressed and non-stressed cells was compared. Strains transformed with plasmids containing stress-responsive promoter::luxCDABE fusions were exposed to sub-lethal levels of stress (pta, grpE, recA, and katG expression was measured). The amount of light produced was indicative of the stress response at the transcriptional level (measured kinetically). Survival was diminished (compared to wild type) in the uspA mutant in all stress conditions regardless of growth phase. However, for the uspE mutant, viability was only affected in stationary (but not exponential) phase cultures for oxidative damage, osmotic shock, and DNA gyrase inhibition experiments. At the transcriptional level, the uspA mutant consistently over-responded to stresses, while the uspE mutant over-responded in the case of grpE (and slightly over-responded in the case of katG) but under-responded in the cases of pta and recA. The irregular pta induction exhibited by the uspE mutant (and therefore the flawed regulation of acetyl phosphate) may lead to decreased motility and aggregation as well as abnormal levels of phosphorylation of response regulators. This could lead to decreased survival to stress in stationary phase; however, it is likely that uspE may have additional functions that have not yet been fully explored.

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