Research Communications

Disease Detectives 

Graduate Student Spotlight: Andrew Kouse and William Broach

April 15, 2011

Spread through water and food, Shigella dysenteriae is one of the most common causes of diarrheal diseases in the world. As the bacteria become increasingly antibiotic resistant, two molecular biology graduate students are studying the secrets of its function. They also hope to learn about the pathogenesis of other potentially fatal bacterial diseases such as E. coli.

Andrew Kouse and William Broach study different aspects of Shigella with Assistant Professor of Biomedical Sciences Erin Murphy in the College of Osteopathic Medicine. Both said they took an interest in the research because of its clinical relevance. “It makes it a little more than basic research,” Broach says.

Broach studies RyhB—a small, non-coding RNA—and how it controls the genes that Shigella requires to cause disease. He looks at environmental factors that tell the organism whether or not it is inside the host, and how the RNA changes gene expression depending on where it is.

Because this particular bacterium only infects humans, Broach uses tissue cultures from a human colon cell line to test the organism’s capabilities. Learning what causes RyhB to signal could enable scientists to block or manipulate those signals.

Kouse focuses on how the bacterium uses the human host as a source for iron, a nutrient essential to Shigella’s survival. By using a protein called ShuA, the bacterium acquires iron from heme, which carries iron through the human blood stream. So far Kouse has learned that Shigella ShuA production increases at higher body temperatures.

“Right now there’s no real vaccine for Shigella and it’s becoming antibiotic resistant,” Kouse says. “If we can make it so it can’t use iron, then we can keep it from growing in the body.”


By Katie Brandt

This article will appear in the Spring/Summer 2011 issue of Perspectives magazine.