Reuters

Members of the Detroit Derby Girls Travel Team battle The Chicago Outfit Syndicate during a women's flat track roller derby bout in Detroit, Michigan, in April 2011.

The women of roller derby are always crashing and smashing into each other, constantly trading bumps and bruises -- and at the same time, they're also trading the microscopic bugs living on their skin. That's according to a new study that used derby to investigate the way contact sports can mix up our skin microbiome. 

"As a derby skater, I was always curious about the unseen ways my teammates influenced me," says Jessica Green, the director of the University of Oregon's Biology and the Built Environment Center, who co-authored the new paper, published online today in the new journal PeerJ. Green is also a former jammer - that's the skater who scores the points - with the Emerald City Roller Girls of Eugene, Ore. (Her derby name: "Thumper Biscuit," she says.) 

"When I was on the track learning a new move - like 'jumping the apex' - my mind would drift to science and 'microbiome land,'" Green says. "I realized that contact sports are an ideal venue to explore if and how touching mediates the exchange of microbes among people in a group setting." 

We know, even if we don't always like to remember it, that our skin is teeming with thousands of kinds of bacteria, and we also know that those microbial communities protect us from pathogens and help regulate our immune systems. But Green and her fellow researchers at the University of Oregon wanted to know more about where we get those microbes, and how those invisible bacterial communities are changed and distributed every time we touch each other.

"For years, most of what we knew about the skin microbiome came from medical studies targeting important pathogens dispersed between sick people and health care staff in a hospital setting," explains lead author James Meadow, a postdoctoral research associate at the University of Oregon's Biology and the Built Environment Center. "This study enabled us to look at whole communities of microbes being passed between healthy people." 

And roller derby -- where players jockey for track position by bumping upper arms, hips or, ah, "booty" (seriously, that's the official roller derby nomenclature) -- seemed like an ideal contact sport to study to find out.

"Over the years I've noticed it's hard to get folks interested in microbes. Maybe it's because you can't see microbes with the naked eye and they are also are misunderstood as being gross," says Green, whose derby past helped with planning the logistics for co-author Keith Herkert, who did the project for his undergraduate honor's project. "Adding roller derby into the mix makes microbes a lot more appealing."

Women from the Emerald City Roller Girls of Eugene, Ore.; the D.C. Roller Girls of Washington, D.C.; and the Silicon Valley Roller Girls of San Jose, Calif., participated in the study, and all skin samples were collected at the Big O Tournament in Eugene on Feb. 10, 2012. All the women were swabbed in the same small area of their upper arm, one area of the skin that is exposed and frequently bumped during a match, or "bout."

After a DNA analysis, the researchers found that teams had similar, distinct microbial communities. "For example, if we had picked a player out at random before they skated in the tournament, I probably could have told you what team she played on," Meadow says. The samples for the D.C. team, for example, contained Brevibacterim, and the samples from the Oregon skaters were similar to the surface samples taken from their home track. But after the teams competed, the hour-long bout mixed up their microbes, leaving opposing teams with more similar-looking microbial communities, the analysis found. Specifically, six different kinds of bacteria - Strepococcus, Sphingomonas, Eubacterium, Porphyromonas, Aerococcus and Methylobacterium - were shared by competing teams after, but not before, the bout.

Next, Meadow and his fellow researchers want to understand how long those similarities last, and how sharing our microbes influences our health in the long term. 

As Green explains it, using roller derby is an easier-to-follow example of how we literally influence each other on a microbial level.  "The people we choose to be in community with -- through sports, work, and social circles -- likely influence our personal biome in ways we never imagined," Green says. 

"Our bodies are home to countless microbes that help define who we are," she continues. "Our health and well-being depend on our microbes. People that have the right cocktail of microbes on their skin, for example, are better positioned to fight off germs or pathogens, because their good microbes out-compete the bad invaders. We currently know very little about where our personal microbial communities come from. Our study suggests that our microbes come, in part, from the people we touch. "

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Kevin Winter / Getty Images file

Your navel is bacteria-land.

What's inside your belly button? Probably dirt and sweat; possibly some lint, and perhaps even a piercing.

But according to new research, which asked 66 men and women to swab their navels with a sterile Q-tip, the skin in study participants' belly buttons also contained an average of 67 different species of bacteria.

The study, published online in the journal PLoS ONE, was done as part of the Belly Button Biodiversity project.

Why belly buttons? "It was a fun way to reach out to the public and teach them about the ecology and evolution of everyday life," says Rob Dunn, PhD, an associate professor of biology at North Carolina State University in Raleigh, who led the study. In other words, the navel is a novel, attention-getting device to study science.

He says the belly button is a fun habitat filled with living organisms that we don't know much about. It's less exposed and gets washed less often than other areas of skin, so the bacterial community in the umbilicus is less disturbed.

Researchers cultured the bacteria from people's navels, and participants could view online photos of the bacterial colonies found living in their belly button. The experimenters also isolated DNA from the sample to identify the exact bacterial species.

In all, they found 2,368 different species of bacteria, which is a heck of a lot of biological diversity.

"We got many more species of bacteria than we expected," says Dunn. But most of those bacterial species were rare ones found in just a few people's belly buttons.

Only about 8 bacterial types occurred in more than 70% of all the people screened.

Those common kinds included species such as Staphylococci, which Dunn says is like your skin's standing army defending it from bad germs. Other frequent microbes were a species of Bacillus, a type that gives stinky feet their odor and may be protecting the body from fungi, and Micrococcus, a hardy bacteria found deep in the navel that can survive without oxygen.

The more common species of bacteria seem to be very predictable, Dunn explains. "They were more frequent and abundant on more people, and more common than we expected," he points out.

Dunn suggests that if scientists can get a handle on those common ones, they will know a lot more about what's going on with skin bacteria. For example, they might understand which ones are really good for the skin and which ones are bad. Or how the bacteria interact with one another or with the immune system.

Two samples contained an extremely rare type of archaea, a single-cell organism never previously found on human skin. One of these samples came from a man who self-reported that he had not bathed or showered for several years -- yikes!

Researchers also collected information from study participants on their age, gender, ethnicity, where they grew up, if they are pet owners (who may get more bacteria on their skin if their pooch or cat frequently lick them), and even if their belly button was an innie or an outie. So far, none of this data has been linked to the types of bacterial species found in someone's umbilicus.

Dunn said his research team will continue to study belly button bacteria and have collected more than 500 samples. But they have also started to look into the microbial diversity of underarms, and they are currently recruiting people interested in sampling the microbial communities found in their homes.

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AP

A clump of Staphylococcus epidermidis bacteria (green) in the extracellular matrix, which connects cells and tissue, taken with a scanning electron microscope. At right, the bacterium Enterococcus faecalis, which lives in the human gut, is just one type of microbe that live on your skin, up your nose, in your gut; enough bacteria, fungi and other microbes that collected together could weigh a few pounds. (AP Photo/National Institute of Allergy and Infectious Diseases (NIAID, Agriculture Department)

Could antibiotics make you fat?

Two studies this week suggest that using antibiotics may save people’s lives, but could also change their metabolisms. Put together, the studies suggest that taking antibiotics might alter digestion to help people absorb calories from food they normally would be unable to digest.

Every human carries pounds of microorganisms that we couldn’t live without. They break down food and extract nutrients like Vitamin K for us. Antibiotics will kill some of these beneficial organisms, which is why so many doctors now tell patients to eat yogurt after taking a course of the drugs, to replace some of the good guys.

“There is emerging evidence suggesting the importance of the microbes in our intestines and their role in absorbing food,” said Dr. Leonardo Trasande of New York University, who led one of the studies.

The two studies look at different sides of the coin, and help answer two questions -- whether antibiotics really do affect how we absorb nutrients, and how they might do so. Together, they support the idea that the drugs kill off some populations of bacteria and allow microbes to flourish that are very good at getting calories out of hard-to-digest plant foods.

Trasande’s team looked at the medical records of more than 11,000 newborns in Britain, who were carefully followed after they were born in the 1990s. The babies who got antibiotics before they were 6 months old were 22 percent more likely to be overweight by the time they were 3 years old, the team reported in the International Journal of Obesity. If they got antibiotics later in childhood, there wasn’t a strong effect – something that could suggest the antibiotics changed the balance of the microbes as they were just setting up shop in the infants. Babies are born with sterile digestive tracts, and they acquire bacteria, yeast and other microorganisms mostly from their mothers. The germs are collectively called “flora” by scientists.

“They play key roles in immune functions, among other things,” Trasande told NBC News. “Antibiotics disrupt the development of the healthy flora in our gut. The earlier the exposure occurs, the more disruptions occur,” Trasande says. “It seems the first few days and months are important. It is difficult to reconstitute that in later life.”

The other piece of the puzzle is whether it’s the antibiotics or something else that is doing this. Dr. Martin Blaser of New York University has been studying the effects of antibiotics on the body for years. A second team he heads has been studying what happens if you feed antibiotics to animals.

They wanted to replicate what farmers have known for decades -- that giving low doses of antibiotics to farm animals make them fatter. Many experts had thought the drugs were keeping the animals from getting infections and making them healthier, but Blaser suspected something else was going on.

When his team gave mice low doses of antibiotics long-term, the mice got fatter even though they weren’t eating any more than other mice. This, they report this week’s issue of the journal Nature, suggests the antibiotics somehow make the mice absorb more calories from their food.

“We have other work that is in process that continues to confirm and extend this,” Blaser said. “That work shows that giving antibiotics early in life, similar to what farmers do in their farm animals, is changing metabolism in mice and making them bigger and fatter.”

The gastrointestinal tract is also the center of hormone production, the researchers said. It’s possible altering the organisms in the intestines – called the microbiome -- could help people better absorb nutrients and calories from “indigestible” foods such as cellulose.

The second NYU team gave the mice varying combinations of the antibiotics penicillin, vancomycin and chlortetracycline. Mice that got the antibiotics piled on more fat than other mice, even though the fatter mice did not eat more. Also, their poop had fewer calories – suggesting they were absorbing more and eliminating less.

Other mouse studies being done by Blaser’s team show that giving antibiotics to mice every once in a while -- akin to giving antibiotics to a child to treat ear infections -- also alter the gut bacteria.

So does that explain why people are getting fatter? Does every dose of antibiotics kill off some bacteria, allowing the energy-efficient species to move in and squeeze every calorie out of an apple peel or bowl of high-fiber cereal?  

“That’s at least one of the mechanisms,” says Blaser. But he notes that studies in people suggest it’s doses very early in life that matter most, just as various colonies of bacteria are getting established in the colon and intestines. And there’s an effect on the immune system, too. Other studies show that changing the balance of bacteria effects immune cells known as T-cells – something that may someday help explain links between diet and diseases such as inflammatory bowel diseases and perhaps even colon cancer.

In other words, it is too soon to say whether a 5-day prescription of Zithromax for strep throat could make you fat.

“A lot of things are interconnected,” Blaser says. “Obesity is multifactorial. I am not saying antibiotic effects on the microbiome are everything but our work suggests it is contributory. Whether it’s 10 percent or 70 percent, we don’t know yet.”

Another big missing piece of the puzzle: Which species of bacteria are the most important? People have trillions of bacteria in and on their bodies. Microbes outnumber human cells by a factor of at least 10 to one and scientists believe at least 10,000 different species live in and on us. Healthy colonies of microbes not only process vitamins, but maintain pH balance on the skin, prevent tooth decay and even protect against infections. So which ones are killed by the antibiotics, and which do we want more of? No one knows yet.

“We are just beginning to scratch the surface,” said Dr. Ilseung Cho, who worked on the study in mice.

While it is important not to use antibiotics when they are not needed, the researchers stress that they do save lives. “I wouldn’t rush to come off any antibiotics right now,” Cho cautioned.

It’s also not clear if food like yogurt, called probiotics, help much. “There is a concept called prebiotics,” Cho said. “It is essentially introducing nutrients into your digestive tract that would select for particular bacteria. Then you might be able to alter the bacteria.”

Prebiotics are found in plain old food such as soybeans, jicama and raw oats, all of which are rich in compounds such as inulin, which people cannot digest, but which certain bacteria love.

Related links:

• Mapping one man's microbes
• Bacteria affect mood
• Ruled by your gut

The "five-second rule" goes something like this: Food dropped on the ground is perfectly sanitary and safe to eat -- as long as it's picked back up within five seconds. But is there any truth to the saying? Nadine Wimmer of KSL, the NBC affiliate in Salt Lake City, decided to investigate.

Wimmer took a bunch of pacifiers and graham crackers -- things mothers and their kids drop all the time -- and placed them on the ground in various places -- in a suburban mom's kitchen and driveway, and under the tables and in the walkways of a local diner. She then took the samples to Richards Laboratories in Pleasant Grove, Utah, where the five-second rule was pretty much debunked.

The kitchen was declared least gross of the four floor spaces, as the crackers dropped on on the kitchen floor showed light to moderate amounts of bacteria, and the pacifiers showed light traces of bacteria, along with yeast and mold. The crackers and pacifiers dropped on the pavement picked up bacteria, plus heavy amounts of mold and yeast. As for the stuff dropped at the diner, the tests showed light amounts of bacteria, yeast and mold on those crackers and pacifiers.

None of the tests found any serious stuff, like salmonella or strep, but "even really common bacteria can make you sick if it catches you in the right condition," says Daniel O'Brien of Richards Laboratories. 

"Five seconds, one second -- it's all the same," O'Brien says. "As far as bacteria's concerned, it's all the same."

Hmm. Agree? What's your stance on the five-second rule?

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