Thallium (Tl) is a heavy metal which causes gastrointestinal irritation and/or peripheral neuropathy through acute exposure and extensive tissue damage through chronic exposure. Sources of thallium water pollution include copper smelting, petroleum refining, and metal mining industries. Thallium behaves as a potassium analog in the cells and has been used as an imaging agent (in nontoxic amounts) for diagnostic imaging of the heart to identify damaged heart cells through the use of sodium/potassium ion pumps (e.g. Na+/K+ ATPase). However, these same cellular mechanisms that make thallium useful in cardiac imagining likely facilitate the accumulation of thallium at toxic levels due to pollution. The purpose of this study is to investigate thallium uptake of Escherichia coli by creating a BioBrick-based plasmid library of endogenous potassium transporter systems Kup and Kdp. This work will help characterize the uptake of thallium at the microbial level in ecosystems polluted by thallium, which will provide a foundation to design effective bioremediation of contaminated areas. Additionally, we aim to create an E. coli mutant with increased uptake capacity by transfection with overexpression vectors of endogenous potassium transport systems Kup and Kdp. We will assess these mutants in the design of a bioaccumulatory technology designed to clean thallium polluted areas. UConn iGEM hopes to provide a genetic engineering solution to a real world problem that currently pollutes our waterways and potentially affects our health.