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Your Bacteria May Be Running Your Life

The bacteria E. coli (here magnified 10,000-fold) are one of the best known inhabitants of the human gut.
Photo by Eric Erbe, digital colorization by Christopher Pooley

The human microbiome. You may never have heard of it before now, but once you know about it, you’ll be hard pressed to stop thinking about it.

Your microbiome is the collection of bacteria (millions of them) that live on and in you. They're in your gut, in your mouth, on your skin. They outnumber your human cells ten to one. And we’ve long known they were important in digesting food and warding off harmful infections.

Now, recent research suggests that your bacteria may be more important than your own DNA in determining your health. There's far more person-to-person variation in microbes than in genetics (we're all 99.9% alike at the DNA level), and there's evidence microbes play important roles in a whole host of health conditions. Obesity? Check. Heart disease and diabetes? Check. Allergies and asthma? Again, check.

But here's where it gets really spooky: gut bacteria appear to affect our brains. Anxiety, depression, and even autism can be linked to microbes. In mice, scientists can turn a timid mouse into a bold one, just by swapping their gut microbiomes via a process known as fecal transplantation (which is exactly what it sounds like, and can be accomplished by ingestion or surgery). Yes, your bacteria may help shape your very personality.

That makes understanding how we end up with the microbes we have, and which combinations work best, rather important, to say the least.

That's why Rob Knight, a professor at the University of Colorado, Boulder and co-founder of both the American Gut Project and the Earth Microbiome Project, has been sampling his own microbiome daily for six years. His wife did the same for a time, and many of their daughters diapers were frozen and analyzed. In fact, when their daughter had to be born by C-section, Knight wanted to be sure she still got the microbiological benefits of an old-fashioned birth, so he innoculated her with a swab of his wife's vaginal excretions.

Sound extreme? Knight says he actually had to be talked into studying himself and his family, but he's come to appreciate the value. Not every volunteer would be willing to do what he's done, and it has provided insights into how stable our microbial communities are, how they become established, and how they evolve over time.

Knight says he never ceases to be surprised and amazed by the sway microbes hold over our lives, but cautions we're still in the early phases of understanding our microbiomes. One of the goals of the American Gut Project, which asks the public to contribute both funding and samples for study, is to simply define "normal" - if such a thing exists - when it comes to microbiomes.

Of course, we've been unwittingly tinkering with our microbiomes for decades, if not centuries. Western microbiomes are notably less diverse than those of hunter-gatherers, and Knight says there are a number of factors likely at play, including overuse of antibiotics, reliance on processed food, even our sedentary lifestyle.

Still, Knight says we're not ready to start engineering our microbiomes just yet. He hesitates to offer advice beyond the standard  - eat fruits and veggies (yogurt and other fermented foods are also on his 'to-eat' list), exercise, and get a good night's sleep. Beyond that, it's all experimentation. Fecal transplants have proven effective for treating a small number of very specific conditions, and it seems likely that our microbes will play a growing role in health care. Wholesale microbial medicine, though, is still a long way off.

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