Dr. Erin Murphy's research focuses on understanding the regulatory mechanisms governing the expression of genes encoding bacterial virulence determinants. In other words, Murphy's research centralizes around bacterial pathways - investigating how bacteria regulate the expression of specific genes in response to environmental conditions encountered within the human host.
"We have more bacteria in and on us than we have human cells," the assistant professor of medical microbiology says. "We rely on these bacteria to help us digest our food and synthesize vitamins, so we are benefiting from bacteria most of the time."
It is the "other" times that Murphy targets, specifically focusing on the bacteria that causes acute diarrheal disease, shigellosis, which kills millions worldwide annually. She is particularly interested in gene expression controlled by non-coding ribonucleic acid (RNA) molecules in response to environmental signals.
"More and more people are learning that these RNAs have a function that's not to encode a protein," Murphy says. "But instead - and this is the case with small RNAs - they act to control the production of other factors. They're regulatory molecules that allow adaptation."
When Shigella bacteria invade a human host, environmental conditions - such as changes in temperature - stimulate a genetic expression pathway within the bacterium that allows it to survive and cause disease. Central to this genetic pathway are certain proteins that promote the production of factors that increase the bacterium's virulence, or its ability to cause illness in its host.
"It's like a domino effect,” Murphy says, noting the disease is much more deadly outside the United States, where access to clean food and water is not always available.
"In the United States, if we get severe diarrhea we can go to the store and get Gatorade," Murphy says. "But if you're already starving to begin with because you don't have access to good food and clean water, then you shigellosis on top of that. And if you don't have good water to rehydrate yourself, that's when the deaths happen."
That's not to say that Americans are not affected. Shigellosis causes a reported 14,000 cases in the United States each year as well. The Centers for Disease Control suggests that the actual number may be 20 times higher, as mild cases often aren't diagnosed or reported.