Portrait of a Grad Student - Janet Lin

My name is Janet Lin, and I’m currently a Master’s student in Dr. Nancy Martin’s lab at Queen’s University. We study the Gram-negative bacterium Salmonella typhimurium, which, similar to E. coli, is commonly associated with foodborne-illnesses. The overall objective of our research is to understand how bacteria are able to sense changes in their external environment and initiate the proper responses for survival/infection. More specifically, we investigate a particular stress-response pathway called the Cpx pathway. This pathway regulates the expression of a multitude of proteins, one of them being a protein kinase called RdoA.

Salmonella lacking the rdoA gene has been found to have lower long-term survival and decreased virulence in the invasion of mice colonic epithelial cells. Based on phosphoproteomic (the collection of all the phosphorylated proteins in a cell) studies done by my labmate Olivia Roque, we have found RdoA to be directly/indirectly responsible for the expression or phosphorylation of a number of proteins. It is clear that the Cpx pathway uses RdoA as an intermediate effector to facilitate bacterial responses further down the pathway. Structurally, RdoA is similar to a group of eukaryotic-like kinases and is highly conserved in over 80 bacterial genera. Despite knowing all this, there are still many questions about this protein kinase that we don’t know. How does RdoA exact these changes in bacterial behaviour? What is/are its target(s) of phosphorylation? What is its mechanism of phosphorylation?

The goal of my research project is to identify functionally-important amino acid residues of RdoA. By mutating specific amino acid residues or regions, we can test whether the mutations have an effect on the kinase’s functionality. My work involves a great deal of fundamental molecular biology such as cloning the rdoA gene into a desired DNA vector and the subsequent overexpression of the protein in a suitable bacterial host. My project has allowed me to be very well-rounded in the repertoire of techniques that I have amassed; I’ve worked with DNA, as well as proteins and RNA. I also interact with undergraduate students as a teaching assistant on a regular basis and help them develop good laboratory techniques.    

For further information, contact Dr. Martin