Author

Da Yae Lee

Publication Date

2014

Document Type

Honors Thesis

Department

Biochemistry

Keywords

Body temperature-Regulation, Intestines-Diseases, Escherichia coli, Virulence (Microbiology)-Genetic aspects, Genetic regulation, Genetic transcription, Thermoregulation, Enteropathogenic E. coli, Virulence gene, Gene regulation, Transcriptomic study, Pathogenic, Environmental cue/stress, Adaptation

Abstract

Bacteria in nature are exposed to a constantly changing physio-chemical environment. As they transit from place to place, abiotic or biotic, bacteria may encounter changes in a number of aspects like temperature, pH, water activity (osmolarity), levels of oxygen, nutrients and toxic substances. Bacteria have developed a sophisticated system of sensing and using temperature changes as gene expression-modulating signals based on conformational changes in temperaturesensitive biological molecules, e.g. nucleic acids, proteins, membrane lipids, etc. Through wholetranscriptome studies, temperature as a sentinel cue in genetic and cellular regulation has been described for a number of microorganisms. According to a number of these studies, human body temperature (37°C) is one of the first cues that invading bacteria sense and respond to upon entry into the human host. Enteropathogenic E. coli [EPEC] is a leading cause of bacterially mediated infant diarrhea in the world and is an important model organism for understanding pathophysiology of the disease. Using RNA-Seq of samples from EPEC E2348/69 adapted to 23°C and shifted from 23°C to 37°C, we detected genes preferentially expressed upon the upshift to body temperature, suggesting their role during EPEC survival and infection in the human body. Genes increased in transcript expression involved an expansive cohort of virulence-associated genes required for EPEC-specific initial and intimate bacterial attachment to host intestinal cells, type III secretion system, and virulence effector proteins. Other genes increased in expression are involved in amino acid and iron utilization and transport, DNA nucleotide synthesis by salvage pathways, and various cellular stress responses including protein chaperoning and refolding. Genes decreased in expression included a large set of metabolism-related genes involved in amino acid biosynthesis, nucleic acid synthesis, carbohydrate and lipid metabolism, and biosynthesis of cofactor thiamin. Additionally, genes involved in translational machinery, flagella motility and pili-associated movement, and acid resistance were reduced in expression. The present study contributes to characterization of body temperature (37°C) as a distinct indicator of host niche and time for pathogenesis. The study also examines bacterial gene regulation as an outcome of an interplay between temperature and other variables like growth medium.

Language

English

Comments

90 pages : color illustrations. Honors Project-Smith College, 2014. Includes bibliographical references (pages 88-90)

Share

COinS