Microscopic visualization of indole signaling in Escherichia coli cells

Abstract

When exposed to antibiotics, some bacteria have been known to adapt and change their own physiology to withstand such adverse conditions. These "persister" cells often shut down cellular functions such as cell division and establish dormancy until conditions are safe again for them to grow and reproduce. For E. coli, the enzyme tryptophanase has been found to be a regulator of such change in physiology. Tryptophanase is an enzyme that breaks down the amino acid tryptophan into products, one of which is indole. Indole is a signaling molecule that may be responsible for inducing surrounding cells to change their physiology and enter dormant conditions. Previous research has found that in E. coli populations, there are a few cell isolates that produce high amounts of indole molecules which are then transmitted to the cells surrounding these isolates. This allows for the cell population to overcome antibiotic resistance as a whole. In this thesis project, a microscopy method has been developed to visualize live E. coli cell isolates interact with each other under antibiotic stress. The successes and flaws of this method are evaluated in the discussion section. Future modifications to the microscopy method are then proposed to further the research into antibiotic persistence.