by Allison Maclachlan, NIGMS
"The skin is an important organ for human health," says Elizabeth Grice, Ph.D., a former NIGMS postdoctoral fellow who did her research in an NIH genetics lab. Our skin is home to about a trillion microscopic organisms like bacteria and fungi. Together, they and their genetic material—their genomes—make up the skin's microbiome.
Grice studies the skin microbiome to learn how and why bacteria live on particular places on the body. Already, she's found that the bacterial communities on healthy skin are different from those on diseased skin. She hopes her work will point to ways of treating some skin diseases, especially chronic wounds.
Grice earned a bachelor's degree in biology from Luther College in Decorah, Iowa, where she studied plant genetics. She received a Ph.D. in human genetics and molecular biology from the Johns Hopkins School of Medicine before coming to NIH to tackle bacterial genomics.
Bacteria aren't all bad. Many are harmless, and some are very helpful. On the skin, they can protect us by taking up space where harmful bacteria would otherwise live.
It might sound unhealthy or even dangerous to have skin that's teeming with bacterial colonies. But your body relies on some of these bacteria as part of its first line of defense. Many bacteria on the skin defend themselves by secreting small proteins that kill harmful invaders. In protecting themselves, they also protect us.
From a study of 20 different skin sites on a group of healthy people's bodies, Grice and her colleagues identified three types of environments: moist, dry, and sebaceous (oily). They then used a new technique to investigate which bacteria colonize what sites.
They found that moist areas tend to host similar bacterial communities in all of the volunteers. The same holds for dry and oily areas. Even with these patterns, skin microbiomes vary greatly from person to person. Your unique pattern depends on things like your age, sex, sun exposure, diet, hygiene, and even where you live and work.
By getting a sense of bacteria on healthy skin, Grice hopes to figure out what's different about the microbes on diseased skin—and maybe even find a way to fix the problem. She's most excited about applying her work to the chronic wounds that are common in people who have diabetes or spend most of their time in beds or wheelchairs.
By studying bacteria on healthy skin, Elizabeth Grice hopes to figure out what's different about the microbes on diseased skin—and maybe even find a way to fix the problem.
A Problem Afoot
Almost 24 million Americans have diabetes, and as many as a quarter of them will get a painful wound known as a diabetic foot ulcer. These are very difficult and expensive to treat. And as obesity rates rise, diabetes—and diabetic foot ulcers—are becoming more common.
She suspects that bacteria make chronic wounds worse because they spur the human immune system to trigger inflammation. Although designed to kill infected cells, inflammation also prevents skin cells from regrowing after an injury.
To investigate what role bacteria play in diabetic wounds, Grice compared healthy lab mice with a group of lab mice bred to display common features of diabetes—like wounds that don't heal well. She found that the diabetic mice had far fewer types of bacteria on their skin than did the healthy mice.
Grice also observed that small wounds on the diabetic mice healed much more slowly than those on the healthy mice.
In about two weeks, most healthy mice looked as good as new. But most diabetic mouse wounds had barely healed even after a month.
Interestingly, bacterial communities in the wounds became more diverse in both groups of mice as they healed— although the wounds on diabetic mice still had less diversity than the ones on healthy mice.
"Bacterial diversity is probably a good thing, especially in wounds," says Grice. "Often, potentially infectious bacteria are found on normal skin and are kept in check by the diversity of bacteria surrounding them."
Grice and her colleagues also found very different patterns of gene activity between the two groups of mice. As a result, the diabetic mice put out a longer-lasting immune response, including inflamed skin. Scientists believe prolonged inflammation might slow the healing process. Grice suspects that one of the main types of bacteria found on diabetic wounds, Staphylococcus, activates inflammation.
Knowing more about the bacteria that thrive on diabetic wounds, Grice and her colleagues are a step closer to looking at whether they could reorganize these colonies to help the wounds heal.
More Than Skin Deep
Grice also spends time studying bacteria that live in the intestines. There, too, microbes can be helpful. Certain strains of E. coli in our digestive tracts help keep dangerous bacteria at bay. They also produce K- and B-complex vitamins, which our bodies can't make enough of on their own.
She is involved with a study of Hirschsprung disease. This is a genetic disorder that leaves parts of the digestive tract without enough nerve endings to push wastes out. Some children born with the disease get a painful inflammation in the gut, but others don't. Together with NIH geneticist Bill Pavan, Grice is looking at gut bacteria to see if their distribution differs between the two groups.
If they find a pattern, it might help predict which patients will need surgery to reduce inflammation.
Taking Exploration Global
Outside of her work, Grice enjoys traveling to exotic locations to soak up the culture. "I really like experiencing different cultures, and science is so multicultural—you get to interact with a diverse group of people," she says.
Now working at the University of Pennsylvania, Grice aims to sustain a successful research program, improve the way chronic wounds are managed, and be a good mentor to students. And she hopes to make time for personal goals like traveling to new continents.