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Publication Date


First Advisor

Christine A. White-Ziegler

Document Type

Honors Project

Degree Name

Bachelor of Arts


Biological Sciences


Escherichia coli, Enteropathogenic, Stress response, pH, Temperature, sRNA, Hfq, Escherichia coli-Genetics, Escherichia coli-Effect of stress on, Escherichia coli-Effect of temperature on, Non-coding RNA-Effect of temperature on, Stress (Physiology), Intestines-Diseases, Hydrogen-ion concentration, Non-coding RNA


Bacteria in nature are constantly experiencing changes in their environment. The key to successful infection depends largely on the pathogens ability to adapt to major changes in their microenvironment and establish colonization. Transcriptome analysis in EPEC has shown that upon environmental stimulation, there are changes in the EPEC transcriptome that accommodate such changes. The expression in genes that relate to stress response, and virulence are significantly upregulated at host temperature and low pH environment. The result also indicates that temperature remains the most important cues. However, the majority of virulence genes are regulated by low pH and not by the host temperature. Our data also shows that sRNA expression changes in response to temperature and pH, and the majority of these sRNA are Hfq-dependent. Thus, transcriptome analysis of EPEC knockout mutant was done to verify the importance of Hfq in EPEC’s adaptation and pathogenesis. Results indicate that virulence genes are significantly down regulated in ∆hfq EPEC. Also, sRNA expression response to temperature and pH cues is also less than those in wild type EPEC. The data supported the idea that Hfq plays an important role in regulating virulence factors in EPEC. Growth curves and viability tests were also done to test the adaptation of wild type EPEC and ∆hfq EPEC in low pH. The result indicated that pH 5.5, which is pH of the caecum where EPEC colonizes, does not affect the growth rate of wild type EPEC or ∆hfq EPEC, while pH 3.0, which is pH of the stomach, significantly lowers the growth rate of wild type EPEC by 3 fold and completely inhibits the growth of ∆hfq EPEC. Thus, Hfq is important for the survival of EPEC at low pH which correlates to transcriptome analysis. ∆hfq EPEC also shows a significant decrease in motility comparing to those of wild type EPEC even though transcriptome analysis does not indicate the correlation between Hfq and motility.


2018 Nhi My Van. Access limited to the Smith College community and other researchers while on campus. Smith College community members also may access from off-campus using a Smith College log-in. Other off-campus researchers may request a copy through Interlibrary Loan for personal use.




80 pages : color illustrations. Includes bibliographical references (pages 76-80)