Your Body Is a Wonderland ... of Bacteria

by Stephanie Pappas 

ENLARGE IMAGE

Microbial megalopolis. The underarm is home to a number of different types of bacteria.

Credit: Veer; Inset image courtesy of Julie Segre

Where can you find your skin's most diverse community of bacteria? Not in a sweaty armpit or linty belly button. According to a new survey of the bacterial ecosystem that covers us, the diversity hot spot of the body's exterior is the forearm. And the surprises don't end there.

Microbes that live in and on our bodies outnumber our own cells 10 to one, but researchers have only recently begun to catalog the residents on our skin. Traditionally, scientists identified human skin bacteria by swabbing volunteers and culturing the samples, but those results skewed toward microbes that grow well in the lab. Thanks to ever-evolving gene-sequencing technology, scientists can now use microbial RNA to identify organisms. With these techniques, researchers have found an unexpectedly wide variety of bacteria on human skin (Science, 23 May 2008, p. 1001). But no one had ever systematically compared bacterial colonies from different areas on the human body.

To do so, scientists from the National Human Genome Research Institute in Bethesda, Maryland, recruited 10 volunteers and asked them to wash with mild soap for 1 week. Then, after 24 hours without bathing, the volunteers arrived at the lab, where researchers swabbed and scraped their skin in 20 places--everywhere from the nostril to the navel to that bane of low-rise jeans aficionados, the gluteal crease. The team analyzed ribosomal RNA from the samples and classified the microbes based on their genomes.

The researchers found about 1000 species total, which were fairly consistent from person to person; it turns out we all have similar tenants in our noses and on our backs. The number suggests that our skin is as variegated as our guts, which house anywhere from 500 to 1000 bacterial species. The team also found vast differences across the skin, according to the study published in tomorrow's issue of Science. Contrary to what acne-prone teenagers might expect, oily areas such as the forehead and scalp are actually less diverse than dry areas such as the forearm (though one is enough for grief: Propionibacterium acnes thrives in oily spots). The most barren region was behind the ear, with a median diversity of 15 species. In comparison, the forearm teemed with a median 44 species. A follow-up with five of the volunteers months later found that bacterial makeup changed little over time.

Why some neighborhoods are more varied than others is unknown. It could be because of skin properties such as hair or oil, exposure to bacteria, or some combination. As for the forearm, geneticist and co-author Julia Segre speculates that exposed arms make a good landing pad for bacteria. Contrasted with how we clean our hands, we rarely lather up our forearms. Whatever the reason, the research shows that location matters. "This paper really highlights that the skin is an ecosystem and that the bacteria that live on our skin are not homogenous," says Segre.

The research "could contribute to explaining why certain skin diseases appear at certain sites of the body and not others," says dermatologist Richard Gallo of the University of California, San Diego. "It's a straightforward description of something that needed to be described." The next step, Segre says, is to investigate the relationship between microbial ecosystems and diseases such as eczema and psoriasis.

Does Porn Watching Lead to Divorce?

He may have been the world's most wanted terrorist at the time he was killed, but it turns out Osama bin Laden was also a typical man. Evidently, bin Laden had an "extensive" stash of porn at his compound in Abbottabad, Pakistan, according to officials.

There's no way to know if the Mrs. -- or the three Mrs. he was evidently living with -- approved of it or even knew. Most people are secretive about their porn habits. Perhaps they may have watched with him although that's doubtful; although more women are watching online porn than ever -- some 13 million American women were checking it out at least once each month in the first three months of 2007 -- they have yet to come close to guys. Women tend to favor cybersex chat rooms -- we like to talk -- while men go for the visuals.

Face it -- if there's a man in your life, he's most likely watching porn and if you're a woman, you're most likely not too happy about it.

I happen to like porn, but a lot of women get tweaked by porn in part because they think their partner is comparing them to Jenna Jameson and other porn stars; we can be competitive -- or insecure -- when it comes to other attractive women, and there's just no way most of us are going to have perfect breasts and butts, and the sexual responses a porn star does. Nor are we necessarily going to be open to all the positions and, uh, broad-mindedness of porn stars (although I'm guessing few of us would turn away, say, a Brad Pitt-George Clooney threesome; I sure wouldn't).

Polls show that we're pretty evenly divided on whether porn is just part of the package when it comes to men and if it's demeaning to women. We're also equally divided on whether porn is bad for relationships, although if you've been involved with someone who's lost interest in having sex with you because he'd prefer to jack off to some online porn, you're pretty clear on the damage it does.

Still, that's a small percentage of porn watchers. The majority of people view their porn watching as some good, not-quite-so-clean fun, according to researcher Alvin Cooper, who heads the San Jose Marital and Sexuality Center and conducts seminars on cybersex addiction. Only 15 percent of the respondents to Cooper's study said their porn watching actually led to behaviors that interfered with their lives.

But what if you happen to be married to someone in that 15 percent? Is that a good reason to dump him? What about the "recreational" porn watchers?

If you read many of the online advice boards, it seems that a lot of women are fed up with their partner's porn watching and wonder if they should get a divorce. According to research by Patrick F. Fagan, senior fellow and director of the conservative Center for Research on Marriage and Religion, pornography is a "quiet family killer."

No only does watching porn contribute to infidelity, but a spouse's porn obsession was a factor in 56 percent of divorces, Fagan says.

Divorce attorneys tend to agree with Fagan's findings. At a 2003 meeting of the American Academy of Matrimonial Lawyers, two-thirds of the 350 divorce lawyers noted that the Internet was playing an increasing role in marital splits, with excessive online porn watching contributing to more than half of the divorces. According to Richard Barry, president of the association, "Pornography had an almost nonexistent role in divorce just seven or eight years ago."

Others aren't so sure, but know something's amiss. "The attention paid to the connection between porn and infidelity doesn't translate into anything like a consensus on what that connection is," writes Ross Douthat, a senior editor at the Atlantic, in "Is Pornography Adultery?" "But if you approach infidelity as a continuum of betrayal rather than an either/or proposition, then the Internet era has ratcheted the experience of pornography much closer to adultery than I suspect most porn users would like to admit."

But is the problem porn itself or a guy's obsession with it? Or is there something else going on?

No man in a healthy sexual relationship would choose porn over bonking his flesh-and-blood partner, says San Francisco Bay Area sex therapist and America's War On Sex: The Attack on Law, Lust, & Liberty author Marty Klein. Emphasis on "healthy." So, if a guy's watching too much porn -- whatever "too" much is and who gets to decide that -- a couple now has an out; they can say he has a "porn addiction." "If a wife claims that porn use is infidelity, if a girlfriend claims that porn use means he isn't attracted to her, a disease is a good place to hide," Klein says.

So what typically happens is she puts her foot down -- "Porn or me!" -- and he promises that he'll stop watching. And some guys actually do stop, Klein says. "The rest will do what they did when they were 14 -- they'll do it in secret, feel bad about it and hope they won't get caught. And so a life of lying about sex continues. You can imagine what that will do to the couple's closeness."

Not help it, and I imagine that's how many couples find themselves divorcing over "porn addiction." What about you?

Vicki Larson

Journalist, daydreamer, freelance columnist

Undoing the Damage of Glaucoma

by Greg Miller 

In people suffering from glaucoma, damage to the optic nerve can slowly degrade peripheral vision and, in the worst cases, eventually lead to blindness. But eyedrops containing nerve growth factor (NGF)--a protein that promotes the survival and growth of neurons in the developing brain--appear to prevent nerve damage in rats and restore some vision in three human glaucoma patients, the authors of a new study claim. Not everyone thinks the reported effect is real, however.

For the study, ophthalmologist Alessandro Lambiase of the University of Rome Campus Bio-Medica and colleagues first mimicked glaucoma in rats. The researchers recreated the most common form of the disease, in which increased fluid pressure inside the eye damages nerves, by injecting saline solution into a vein in the eye. They kept the intraocular pressure up for 7 weeks, killing about 40% of the neurons in the retina whose tail-like axons give rise to the optic nerve, which conveys visual information to the brain. However, in rats treated four times daily with NGF-laced eyedrops during the 7-week period, the death of these "retinal ganglion cells" was reduced by about 25%, the team reports online today in the Proceedings of the National Academy of Sciences. (The senior author on the paper is neuroscientist Rita Levi-Montalcini, who shared the 1986 Nobel Prize in physiology or medicine for the discovery of NGF and in April became the first Nobelist to celebrate a 100th birthday.)

Encouraged by these findings, the researchers asked three patients with advanced glaucoma to take the drops four times daily for 3 months. Peripheral vision, one of the main visual functions impaired by glaucoma, improved in two of the patients and got no worse in the third, the researchers report in the same paper. They also report improvements in visual acuity, contrast sensitivity, and in electrophysiological measures of nerve conduction in the visual system in some or all of the patients.

Experts are divided over the findings. "It's very significant if it's real," says Richard Libby, a glaucoma researcher at the University of Rochester in New York state. Other compounds have been shown to have a similar protective effect on rat retinal cells when injected into the eye, Libby says, but the possibility of delivering a neuroprotective drug in eyedrops is "very exciting."

But Harry Quigley, an ophthalmologist and glaucoma researcher at Johns Hopkins University in Baltimore, Maryland, isn't buying any of it. Quigley faults the study's methods, including the lack of human control subjects and the design of the human experiments. Visual field measurements are notoriously susceptible to placebo effects, Quigley says, and because subjects knew they were getting the real treatment, he thinks it's possible the improvements in peripheral vision were due to raised expectations rather than the drug itself.