Bowdoin Geneticist, Students Pioneer Knowledge of the Mighty Mite

Story posted June 24, 2010

michael palopoli
Associate Professor of Biology Michael Palopoli

The way Mike Palopoli sees it, we're all perfect hosts.

Not the come-in-put-your-feet-up-have-a-drink kind of hosts. More the egg hatching, plasma slurping, leg wriggling variety.

Palopoli is an evolutionary geneticist who is studying mites. For the past several years the Bowdoin Associate Professor of Biology has been taking swipes at willing foreheads at his Bowdoin laboratory to get tiny samples of the follicle mites that live inside all our pores.

"We have at least two species of these things that live in our pores, that's their natural habitat," notes Palopoli. "We're studying their genetic variations to try to determine where the mites come from, and within our species, how often mites are moving between people."

follilcle mite
Colored scanning electron micrograph of the follicle mite, Demodex folliculorum.

The species of mite Palopoli studies, Demodex folliculorum, lives inside human hair follicles, especially on the skin of the face. They are believed to feed on oily secretions from the skin's sebaceous glands, as well as dead skin cells. Infestation with follicle mites is probably universal and usually symptomless, says Palopoli, though some individuals may develop allergic reactions or skin rashes, particularly if they have compromised immune systems.

Palopoli's lab, which is fueled by Bowdoin student research assistants, is the first ever to sequence the mites' DNA. "That's part of the reason I decided to study them," he says. "I thought, that's interesting: We've got things living in our skin that nobody really knows anything about."

Have they always lived there? How do they arrive? How do they affect us?

Palopoli is comparing genetic variations within mites from one host vs. multiple hosts, to develop inferences about how often mites may move between hosts. That's where his human samples come in handy. The data collection, which is done with informed consent and in accordance with protocol approved by the College's Research Oversight Committee, is a quick procedure—a painless little swipe with the sterilized end of a bobby pin.

Roughly 40 people have been sampled, including multiple members from three families. One of those is Palopoli's own family.

students in palopoli lab
Student researchers Van Tra '13, left, and Dorothy Pei '11, right, are doing ongoing research in Palopoli's lab.

"That made for an interesting visit with my parents," he says, smiling. "I brought along a microscope and all the necessary supplies and was able to show my parents a bunch of their own mites on a glass slide, ready to be sampled for DNA.

"At a genetic level," he adds, "It turns out that my parents and I have very similar mite populations, suggesting that I probably got my mites from my parents—especially my mom. Based on our results, it appears that we tend to get more mites from our mother than we do from our father."

Based on differences among the samples, it also appears that geography may play a big part in determining the mites that live on our foreheads.

"We do have some evidence that there is significant geographic variation in mite genetics," notes Palopoli. "Some students who were born and raised in other countries before coming to Bowdoin have volunteered to provide us with mites. In comparison with mites we get from Americans with recent European ancestry, they are quite distinct. It suggests that people from different parts of the world carry genetically distinct mite populations. Variation in mite DNA could even prove useful for tracking historical human migration patterns."

What remains unclear is whether you can contract or exchange mites from physical contact. "Students have thought up clever tests for this," says Palopoli.

Does it have anything to do with Ivies or Spring Break?

palopoli with student
Student researcher Alicia Satterly '10, left, shares a story with Palopoli.


Palopoli chuckles. "Well, we can say one thing: Exchange students who have spent a year or two or three here, they still have their own distinctive mites. Clearly, the exchange that is happening is not all the time and universal."

It might seem like a lot of bother for a frankly creepy critter, but Palopoli's investigations may have broader practical implications.

Certain skin disorders, including rosacea, are associated with high densities of these mites. They also are known to proliferate in individuals with compromised immune symptoms, such as AIDS patients and people undergoing chemotheraphy.

"Down the road it would be wonderful if we could establish a collaboration with a medical doctor to sample patients with rosacea to see if their mites are distinct," says Palopli. "Is it a pathogenic strain or an issue with how their skin is reacting to the mites? It is also possible that these mites could carry other diseases along for the ride if they move between hosts.

"The exciting thing is that we now have the tools to begin to ask those kinds of questions."

Palopoli's research on follicle mites is supported by the Arnold and Mabel Beckman Foundation, and from the National Center for Resarch Resources, as well as awards from the Howard Hughes Medical Institute and NASA.

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