OHSU scientist Justin Merritt, Ph.D., is captivated by tiny, microscopic bugs.
“It’s fascinating to me that you have bacteria, which are single-celled organisms, and they can cause chaos in something as complex as a human being,” he said.
Many bacteria are beneficial to human health, but others can lead to a long list of diseases, ranging from cholera to diphtheria and even tooth decay.
Merritt, an associate professor of restorative dentistry in the OHSU School of Dentistry, studies the bacteria Streptococcus mutans, or S. mutans for short. The microbe normally exists in small amounts inside human mouths. But, when people eat a lot of sugar, it can become abundant and create an environment that promotes cavities and other oral diseases.
S. mutans produces a lot of lactic acid as it ferments sugar, which makes the surfaces of teeth more acidic. Such an acidic environment also enables it to outgrow other, beneficial microbes. As it proliferates, the acid it produces gradually eats away at tooth enamel and leads to cavities.
Scientific inspiration
Merritt has been interested in science since he was very young. He majored in microbiology and immunology as a pre-med undergraduate at the University of Miami, but never left biology for medicine.
Merritt started studying S. mutans in 1999 as a graduate student at the University of California Los Angeles, from which he earned a doctorate in molecular biology in 2004. As a result, he’s spent nearly two decades understanding the many molecular mechanisms that trigger bacteria to cause oral disease. He joined OHSU in 2014.
In recent years, many human diseases have been linked to disruptions in the bacteria that naturally exist in the body, which is called dysbiosis. Among dysbiotic diseases, digestive disorders are the most commonly recognized, but Merritt points out the connection between oral dysbiosis and oral disease has been studied for decades. Oral bacteria are better understood than any other microbes in the human body, he said.
“What gum disease has to do with irritable bowel disease isn’t obvious to the general public,” Merritt said. “But as we learn more about oral bacteria, it could one day lead to better treatments for all types of dysbiotic diseases.”
Mystery solver
As many seasoned scientists know, Merritt’s typical workday doesn’t include a lot of quality time with petri dishes anymore. He oversees a lab that employs four postdoctoral researchers, two senior scientists and one visiting scientist.
His days are often spent analyzing data from experiments others conducted in his lab and hypothesizing about what the data means for the various way bacteria cause oral disease. He is the lead investigator on two projects funded by the National Institute of Dental and Craniofacial Health, a branch of the National Institutes of Health, and is the co-lead investigator on a third. He also serves as an associate editor for the journal Frontiers in Cellular and Infection Microbiology.
But whatever his role in research is, he relishes the ongoing pursuit of science.
“I love mysteries,” Merritt said. “I can’t stand knowing one tidbit of info and not knowing why something happens. I get obsessed with finding answers. Of course, every time you find an answer to something, it creates another question.”