Portrait of a Grad Student - Lisa Starr

Project name: Regulation and natural function of the MexAB-OprM multi-drug efflux system of Pseudomonas aeruginosa

My name is Lisa and I’m a Master’s student in the Poole lab. In our lab, we study Pseudomonas aeruginosa, a Gram-negative opportunistic bacterial pathogen that can infect immunocompromised people. Cystic fibrosis patients are especially susceptible to P. aeruginosa infections, which often lead to respiratory failure and death. These infections are difficult to treat due to the emergence of resistant strains during antimicrobial treatments.

One of the ways that P. aeruginosa is resistant to antibiotics is through active export of the drugs via multi-drug efflux systems, several of which have been identified. This makes treatment of P. aeruginosa infections especially difficult because these efflux systems are able to export drugs that the bacteria have never even been exposed to.

I am studying the effect of various environmental contaminants such as pentachlorophenol (PCP) on the regulation of one multi-drug efflux system, MexAB-OprM. In particular, I am looking at how two regulators of mexAB-oprM gene expression, NalC and PA3719 are affected by contaminants. For example, an interaction between NalC and PCP seems to cause overexpression of PA3719, resulting in overexpression of MexAB-OprM and increased resistance to many clinically important antimicrobials.

In my research, I use semi-quantitative RT-PCR to assess gene expression in the presence of contaminants. I also use electromobility shift assays to determine the effect of contaminants on regulator binding to DNA promoter sequences. To determine whether the mexAB-oprM promoter is being activated in the presence of contaminants, I am fusing the promoter to a reporter gene, inserting it into the chromosome of P. aeruginosa and performing a luciferase assay.

For further information, contact Dr. Poole