Author ORCID Identifier

0000-0001-9179-3875

Date of Graduation

12-2018

Document Type

Dissertation (PhD)

Program Affiliation

Microbiology and Molecular Genetics

Degree Name

Doctor of Philosophy (PhD)

Advisor/Committee Chair

Dr. Jiqiang 'Lanny' Ling

Committee Member

Dr. William Margolin

Committee Member

Dr. Kevin Morano

Committee Member

Dr. Jeffrey Frost

Committee Member

Dr. Francis Tsai

Abstract

Bacterial populations grow clonal populations; however, individual cells have a variety of phenotypes. The physiological heterogeneity observed in populations has been attributed to variations in the processes of gene expression. For example, promoter expression has been shown to be heterogeneous within a population and contribute to increased stress tolerance in a subpopulation of cells. In comparison to transcription, the influence of translation on single cells is unclear. In this study, my collaborators and I have developed a dual-fluorescence reporter that allows us to measure the mistranslation rate in single cells in vivo. Using this reporter, we found that mistranslation rates are heterogeneous in bacterial populations. Additionally, our work has provided insights into the mechanisms that affect mistranslation rates in vivo, such as overall protein synthesis rates and the activity of release factor proteins.

The accuracy of protein synthesis has a significant effect on bacterial physiology. Severe increases in mistranslation result in the accumulation of misfolded proteins that can be detrimental and lethal to the cell. Despite the cost of errors during translation, the process of translation is error-prone in comparison to other processes of gene expression. Surprisingly, a number of benefits have been found as a result of mistranslation including increased oxidative stress and antibiotic tolerance. My research has found that the heterogeneity of mistranslation in a population results in a subpopulation of cells that recover quickly from starvation. Additionally, in a population-based study, I have found that the mistranslation-induced heat shock response is not detrimental and, instead, protects cells from future lethal heat stress. Together, this study characterizes the heterogeneity of mistranslation in single cells for the first time and identifies the beneficial role mistranslation can have in single cell and population-based physiology.

Keywords

Mistranslation, Single Cell, Heterogeneity, Escherichia coli, Heat Shock, Starvation

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