Publication Date

2015

Document Type

Honors Thesis

Department

Biochemistry

Keywords

Escherichia coli, Escherichia coli-Effect of stress on, Biofilms, Body temperature-Regulation, Urinary tract infections, E. coli, Termperature

Abstract

Bacteria in nature are exposed to a wide range of conditions as they transit through biotic and abiotic environments. Bacteria have developed complex mechanisms to sense and react to their constantly changing environments. One key regulatory cue for bacteria is temperature. Temperature can be used to alter gene expression through conformational changes in temperature sensitive molecules such as nucleic acids, protein and lipids. Temperature has been shown to be an important cue through whole-transcriptome studies of a variety of microorganisms. Human body temperature (37°C) has been shown to be an important cue for pathogenic bacteria, allowing them to sense their entry into the human host and respond accordingly. Uropathogenic Escherichia coli (UPEC) is a leading cause of urinary tract infections (UTIs). In hospitals UTIs are often associated with catheters, as bacteria can form biofilms in catheters and more easily access the urinary tract. Because of this we became interested in the mechanism of biofilm formation in UPEC at temperatures that bacteria might encounter in the environment (23°C) compared to those encountered in the human host (37°C). This study seeks to understand the role temperature and RpoS, the stress response sigma factor, play in biofilm formation in urinary tract infection forming bacteria. To elucidate the genes involved in the temperature regulation of biofilms, a biofilm formation assay and RNA extract from biofilms will be used. Additionally, this experiment will also further examine the role of RpoS, a sigma factor that is known to regulate the planktonic vs. biofilm transition in commensal E. coli. This study found that genes involved in motility are more highly expressed in planktonic cells and in biofilm cells grown at 23°C than in biofilm cells grown at 37°C. Genes associated with surface attachment show diverse patterns in relation to temperature but all show different expression in terms of temperature and RpoS. Other genes involved in the production of biofilm, such as those that code for colonic acid, K1 capsule, and cellulose production all show differential expression at the two different temperatures. Genes that encode the PGA extracellular matrix appear to be expressed at the same level at both temperatures, under both growth conditions, and regardless of the functionality of RpoS. This study shows that high temperature increases adhesins that are involved in the formation of intracellular biofilms whereas low temperature increases adhesins involved in surface attachment and bacterial cell aggregation.

Language

English

Comments

72 pages : illustrations (some color). Honors project-Smith College, 2015. Includes bibliographical references (pages 66-72)

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