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Researchers Explore Bacteria in the Mouth

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Researchers are exploring the microscopic jungles of bacteria found all over the human body, especially in the mouth. It's a landscape teeming with bacteria that help determine whether your teeth fall out or stay pearly white.


Scientists have tramped through deserts, forest and bogs for hundreds of years now, looking for living organisms as well as fossils. That's why we know so much about the things that live inside these ecosystems. Now, researchers are exploring ecosystems that are more mysterious and much harder to get into.

For today's Science Out of the Box segment, we consider one of the microscopic jungles of bacteria found all over the human body.

(Soundbite of music)

SEABROOK: Your mouth is a landscape teeming with bacteria that helped determine whether your teeth fallout or stay pearly white.

NPR's John Nielsen has more on the emerging field of microscopic ecology.

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JOHN NIELSEN: Lawrence Siu, a dentist in Tacoma Park, Maryland, says he has seen teeth and gums so rotted out that they would shame a zombie.

Dr. LAWRENCE SIU (Dentist): A 32-year-old gentleman sat down here and had incredibly severe periodontal disease where he was basically going to lose all his teeth, and that's a very young age especially today; most 32-year-olds have great teeth.

NIELSEN: Especially if they brush and floss religiously like this guy says he did. Why good brushers sometimes get zombie mouth is a big mystery, but some researchers hope to solve it by exploring the human mouth like ecologists explore a forest. They are mapping the habitats inside your mouth, identifying the species living there and figuring out what makes these species thrive or die.

Researcher Bruce Paster says it's not an easy job.

Dr. BRUCE PASTER (Researcher, Forsyth Institute): In your mouth, for example, there's 10 to 50 billion oral bacteria present.

NIELSEN: Paster is a microbiologist at the Forsyth Institute in Boston, Massachusetts. He says it used to be impossible for scientists to identify most of the bacteria inside humans because the bugs died whenever scientists tried to culture them outside the body. Then came the genetic revolution, it gave scientists, like Paster, the tools they needed to start naming and mapping different species.

Dr. PASTER: And in, perhaps your mouth, you have about 75 to a hundred different species.

NIELSEN: Paster says it turns out that these species tend to congregate in certain kinds of habitats just like bears tend to end up in certain kinds of forests.

Dr. PASTER: If you look at bacteria on the sides of the tongue, they're a little bit different than the top of the tongue, and the same thing goes with the cheek and the hard palette and the teeth.

NIELSEN: Paster spent a lot of time exploring on habitat that is very interesting to dentists, the so-called gingival pocket found between the teeth and gums. He says you'd see amazing things if you could sail a microscopic submarine down into the bacterial batter in that part of the mouth.

Dr. PASTER: If you shrunk yourself, you would see all different shapes and sizes of bacteria. There are round forms called cocci, and these rods. There are bacteria which move around very rapidly, so you'd have to - if you're down in there, you'd have to watch out because this bacteria would speed by you. They look like little propellers sometimes; other ones look like giant corkscrews that corkscrew through the batter.

NIELSEN: The fast-moving corkscrews and propellers are bacteria that can rot your teeth and gums out, if they can find a place to land and thrive. But this is where it gets really interesting. When this ecosystem is healthy, Paster says it's shielded by a thick forest of bacteria that prevents the bad guys from even touching down.

Dr. PASTER: They have a crude way of communicating with one another. They know for example that, oh, wait, I've grown too much, I'll stop my growth, or, I'm not growing enough, I'm going to grow more.

NIELSEN: Paster says ecosystems much like this one are now being mapped out and surveyed all over the body - in the nose, on the skin, and especially in the gut. If scientists could learn how to keep them healthy, Paster thinks they'd learn how to keep a lot of people healthy in the process.

Abigail Salyers, a microbiologist at the University of Illinois at Champaign Urbana says it's the kind of work that makes you rethink what a human being is.

Dr. ABIGAIL SALYERS (Professor, Microbiologist, University of Illinois, Urbana-Champaign): One way we're thinking of it is that humans are bacterial planets, and the bacteria constantly modifying us as we're constantly feeding them, and it's a dynamic association. And we really to understand that better in order to understand health and disease prevention.

NIELSEN: Someday, these microbial explorers might design a test that tells you whether the habitats in your mouth are in good shape or not. If they're not, it might someday be possible to repair the damage by injecting the right kind of bacteria into the right place. Maybe that will help prevent an unexpected case of zombie mouth. But at the moment, all of that is still hypothetical, which is why good dentists all say you need to play the odds and keep on flossing.

John Nielsen, NPR News, Washington.

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